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A wheelist
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Discussion Starter · #1 ·
I received a custom cyclocross frame 7 rides ago (meaning I have the input from 7 rides on the new bike) and I am not happy with the steering and I suspect that I have too much Trail.

Here is what I know -

Head angle - 72 (builder's info).
Fork - Ritchey WCS cyclocross - rake 48mm (Ritchey site specs).
Wheel radius - 353mm (Challenge Grifo Dry clincher).
Tire profile - 32mm.

From the Excel trail calculator I get a Trail of 64.2mm.
From many home measurements (string, plumb line) I get a measured trail of between 67 and 70mm.

I'm using the bike for an 70% dirt road rider, 30% paved.

What I'm experiencing is this - the bike wanders as I'm riding down hard-packed dirt roads (and paved) and if the surface gets in any way a bit loose and I make a steering correction or attempt the slightest turn the front end wants to wash out and the tire slide. It seems that the bike has to lean too much and needs a big steering angle input to effect the turn or correction.

If I try a slow (sub walking pace) U-turn on a dirt road, the headtube wants to flop over and the tire slide.

I'm coming from a custom mountain bike frame (Seven) with a 72 degree head angle (ordered by me and steep for a mtb) and a rigid carbon fork. It steers and handles like a dream. I've had it nine years.

Can any frame builders help with an opinion? Have I got too much trail? Do I need a 73 degree head angle CX frame with that fork?

All I can put this down to is too much trail and head tube flop. This is weird as most CX frames seem to spec a 72 degree head angle and the Ouzo Pro CX fork is even LESS rake (= more trail) than my Ritchey WCS.

Help!! I need info and opinions before I call the builder.

I had this same issue years ago (15) with a Bontrager mtb frame and Keith's rigid fork with his vision of a short rake/long trail. That thing would wash out brutally on loose corners while guys on factory (much cheaper) bikes would pass me on the inside while I was sliding for the weeds. Keith sent me a longer rake crown and the problem was solved overnight.
 

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It depends...

Honestly, sounds more like a weight distribution issue to me - not enough weight on the front wheel, maybe? Anything from 60-70mm of trail is pretty "normal" for a cyclocross bike - the numbers can be all over the map for head angle and fork rake, really. Just a matter of preference. 64mm (or 67, though I really don't think a plumb line and string/ruler are going to be accurate enough to measure the trail very well) is not unusual for a 'cross bike at all.

How does the chainstay and toptube length compare to your mountain bike? Have you talked to the builder? If so, what did he/she say? Is this your first cyclocross bike, or if not, what others have you had and liked?

FWIW, I do quite a few CX bikes and tend to do something around 71.5-72 HTA and 43-45mm of rake - so trail numbers in the high 60s/low 70s. That's what I ride myself, too, and it seems fine to me. That's not to say you're wrong about not liking how the bike handles, I just mean that you might want to look for other culprits before blaming the trail number.

-Walt

Mike T. said:
I received a custom cyclocross frame 7 rides ago (meaning I have the input from 7 rides on the new bike) and I am not happy with the steering and I suspect that I have too much Trail.

Here is what I know -

Head angle - 72 (builder's info).
Fork - Ritchey WCS cyclocross - rake 48mm (Ritchey site specs).
Wheel radius - 353mm (Challenge Grifo Dry clincher).
Tire profile - 32mm.

From the Excel trail calculator I get a Trail of 64.2mm.
From many home measurements (string, plumb line) I get a measured trail of between 67 and 70mm.

I'm using the bike for an 70% dirt road rider, 30% paved.

What I'm experiencing is this - the bike wanders as I'm riding down hard-packed dirt roads (and paved) and if the surface gets in any way a bit loose and I make a steering correction or attempt the slightest turn the front end wants to wash out and the tire slide. It seems that the bike has to lean too much and needs a big steering angle input to effect the turn or correction.

If I try a slow (sub walking pace) U-turn on a dirt road, the headtube wants to flop over and the tire slide.

I'm coming from a custom mountain bike frame (Seven) with a 72 degree head angle (ordered by me and steep for a mtb) and a rigid carbon fork. It steers and handles like a dream. I've had it nine years.

Can any frame builders help with an opinion? Have I got too much trail? Do I need a 73 degree head angle CX frame with that fork?

All I can put this down to is too much trail and head tube flop. This is weird as most CX frames seem to spec a 72 degree head angle and the Ouzo Pro CX fork is even LESS rake (= more trail) than my Ritchey WCS.

Help!! I need info and opinions before I call the builder.

I had this same issue years ago (15) with a Bontrager mtb frame and Keith's rigid fork with his vision of a short rake/long trail. That thing would wash out brutally on loose corners while guys on factory (much cheaper) bikes would pass me on the inside while I was sliding for the weeds. Keith sent me a longer rake crown and the problem was solved overnight.
 

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A wheelist
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Discussion Starter · #3 ·
Walt said:
Honestly, sounds more like a weight distribution issue to me - not enough weight on the front wheel, maybe?
Good question and I don't know the answer. The CX is very close in dimensions to my roadbike (1 deg slacker HA) as this CX bike was always intended to be a Dirt Road Bike and therefore not much changed from my roadie. The builder (N.Am's most prolific custom builder over the past 34 years) agreed to the specs for my CX and injected his own normal 72 CX-bike HA. The reach (saddle center to hoods) is the same on all three bikes - CX, road, MTB.

Anything from 60-70mm of trail is pretty "normal" for a cyclocross bike - the numbers can be all over the map for head angle and fork rake, really. Just a matter of preference. 64mm (or 670
From what I gather from researching CX frames for months before I ordered mine, 72HA and the built-in rake of carbon forks seems to be the norm. That's why I never questioned the HA. That's the only spec that I didn't have input on. I just let the builder get on with that one. Heck how many CX frames deviate from 72? None? I'm talking "medium" sized frames now.

How does the chainstay and toptube length compare to your mountain bike?
The CS of the CX is 1/2" shorter than the MTB. Fatter tires are the issue there. TT - the MTB is a few cms longer but then there isn't handlebar reach to worry about. The reach from saddle to grip is within 0.5cm on all three bikes

Have you talked to the builder? If so, what did he/she say? Is this your first cyclocross bike, or if not, what others have you had and liked?
No I haven't talked to him yet as I wanted to get some opinions. I have the experience of ONE cx bike while he (and others) have the experience of hundreds.

But what I *do* have experience of is two frames in my history that had the same traits as this bike - the worst one was a Kestrel carbon mtb frame that was a mid-80s design (ie - short rigid fork) and were being sold in the late 90s when people (me included) were stuffing suspension forks under them. I wondered why that thing steered like a chopper. I eventally found that the fork (jacking up the headtube) gave it a HA of 68 while it was advertised at 72. The Trail was 2x (over 4") the acceptable figure.

My new CX has traits very similar to that mtb frame.

FWIW, I do quite a few CX bikes and tend to do something around 71.5-72 HTA and 43-45mm of rake - so trail numbers in the high 60s/low 70s. That's what I ride myself, too, and it seems fine to me. That's not to say you're wrong about not liking how the bike handles, I just mean that you might want to look for other culprits before blaming the trail number.
I hear ya on the specs and I haven't found any specs that are much different. It just that the handling doesn't seem right to me. :confused:

Thanks for your input Walt.
 

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Interesting issues

Some ideas to try:
-Put a fatter set of tires on the bike. It could be that you're just not used to riding (relatively) skinny tires on dirt. This will slightly increase the trail, so if it feels better with fatter tires, high trail probably isn't the problem.
-Measure the actual angles of the bike. It *could* be (though I'd be very surprised) that the head tube angle isn't actually 72 degrees. Wheel flop usually doesn't become noticeable at low speeds (to me) until the trail gets up over 90mm or so, so I'm surprised that you're noticing wheel flop.
-Put your CX wheels on your road bike and go ride it on the dirt (if your brakes will clear the tires), to see if lower trail is actually what you want.
-Call the builder and see if he/she has any ideas for you. You may end up needing a custom fork with more rake, or perhaps one with less rake. Hard to say. It does sound like you should see if you can find some other CX bikes to try - it might be that conventional CX geometry just doesn't agree with you.

Good luck!

-Walt
 

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A wheelist
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Discussion Starter · #5 ·
Walt said:
Some ideas to try:
-Put a fatter set of tires on the bike. It could be that you're just not used to riding (relatively) skinny tires on dirt. This will slightly increase the trail, so if it feels better with fatter tires, high trail probably isn't the problem.
Yeah could be I'm not used to skinny tires but it still wanders vaguely on paved roads and feels like the head tube flops over when I do a slow speed U.

Measure the actual angles of the bike. It *could* be (though I'd be very surprised) that the head tube angle isn't actually 72 degrees.
I did since my first post. I have an angle finder and a 3' level. I found the most level piece of cement floor. Of course the angle finder graduations are awully close but it looks to be 71 degress.

Wheel flop usually doesn't become noticeable at low speeds (to me) until the trail gets up over 90mm or so, so I'm surprised that you're noticing wheel flop.
90mm? :eek: :eek: :eek:

Put your CX wheels on your road bike and go ride it on the dirt (if your brakes will clear the tires), to see if lower trail is actually what you want.
That certainly won't work on the rear and maybe not on the front. I can squeak a 25mm tire in the rear and that's it. I'd thought of putting my road bike front wheel in the CX and the 23mm tire (much lower profile) will steepen the HA a touch. This will reduce the trail. It will be interesting to see if I feel any difference with the wandering. Of course with its smooth tire I won't get any lateral traction on the dirt.

Call the builder and see if he/she has any ideas for you. You may end up needing a custom fork with more rake, or perhaps one with less rake. Hard to say.
What I really need is one with a variable rake but that ain't gonna happen.

It does sound like you should see if you can find some other CX bikes to try - it might be that conventional CX geometry just doesn't agree with you.
I don't know one other person with a CX bike except for a tiny ladies' Jake that I mechanic occasionally. I can't even test ride it when I tune it.

Good luck!
Thanks. I'm gonna need it.
 

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Keep us updated

I'll be interested to hear what you figure out. Honestly, I'm stumped. If the HTA is really 71 (it's hard to be too sure with an angle finder), then trail is probably pushing up into the high 60s/low 70s, but that's not out of line for a CX bike.

-Walt
 

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A wheelist
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Discussion Starter · #7 ·
Walt said:
I'll be interested to hear what you figure out. Honestly, I'm stumped. If the HTA is really 71 (it's hard to be too sure with an angle finder), then trail is probably pushing up into the high 60s/low 70s, but that's not out of line for a CX bike.
-Walt
Oh don't worry; I'll keep ye updated alright. With having two nightmarish long trail bikes in the past (Kestrel & Bontrager) and hating them and knowing what a steep HA mountain bike feels like (my 72 degree Seven) I'm on a bit of a mission with this new frame. I just can't see where the vagueness is coming from though.

If I could lay my hands on a cheapo 1.125" steerer steel CX fork I'd bend that thing to give me a bit more rake (and less trail) to see how that would feel. Maybe I'll take a look on e-bay.

Have a look at my bike here Walt to see if the geom looks normal to you. I can send a pic with it on hard ground if that will help.
 

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Discussion Starter · #9 ·
I'd slide your saddle forward. Get a bit more weight on the front. You've not mentioned seat angle, seat position and I think those are crucial in this case.
This custom framed CX bike is setup very close to my road bike setup and my mountain bike. My mountain bike is used mainly on the same dirt roads where I now use the cyclocross bike so it's a real roadified mountain bike.

The cyclocross frame was, of course, designed around my measurements. The SA of 74 degrees, is based on my femur length and whatever else the custom builder factors into it. This custom builder has made more frames than anyone in N.America in since their startup in '75 (33 years). The 74 SA on the CX is .5 degrees steeper than the 73.5 STA on my road bike (carbon Argon18). The HA of the CX bike is one degree slacker than my road bike's 73 degrees.

I just did a "sight across" where I stood my roadiebike and CX bike side-by-side, stood back 20' and sighted through the frames. That's a great way to see relativity between two bikes.

The seat tube angles & saddle position are dead on (CX spec 74, RB spec 73.5). The HTA on the cyclocross (spec 72) is slacker than the road bike (spec 73). My bars are slighly up and back on the CX from the road bike (and supposed to be!).

So apart from my hands being slightly higher and rearward on the CX compared to the RB, everything is the same.

In my string and plumbline measurement of Trail on both bikes I get 67-70mm on the CX and 50mm on the RB. The CX wheelbase is 1.25" longer.

So my main deduction is that the Trail is about 17-20mm greater on the cyclocross frame than on my roadie. I did a ride on the cyclocross bike today that I can duplicate on my roadbike if I throw on some 25mm tires. That will be interesting.
 

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cheapo fork

Mike T. said:
If I could lay my hands on a cheapo 1.125" steerer steel CX fork I'd bend that thing to give me a bit more rake (and less trail) to see how that would feel.
You could pick up one of these just to try it out... it's got 50mm of rake, which you could increase or decrease as a test!
 

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Discussion Starter · #11 ·
ong said:
You could pick up one of these just to try it out... it's got 50mm of rake, which you could increase or decrease as a test!
I found these on fleabay. But then it's $30 shipping up here to Canada. I'll check Universal's shipping to see which is the cheaper deal. I have a friend who's built a few frames; I'll check to see if he has a fork blade raker. Those canti bosses won't do well on a regular blade raker I don't think. I guess for a crude test job I could just use the vice.
 

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As already mentioned, the 72 head angle and high 40s fork is standard issue for cross bikes.

With a 74 seat angle I don't suspect it's weight distribution either, though it could possibly be improved with longer stays and a shorter top tube. You mention the reach is the same as your road bike, so that makes me wonder if that's a little bit long. Not "the builder f'ed up" long, but "maybe next time we'll try shorter" long.

One thing that might be part of it is your tires - the Grifo Dry is a file tread and they're going to be squirrely on anything loose. Especially if you're running a lot of pressure in them. Assuming you have room to experiment, try running the tires a little softer, and if that's working for you then take it a little further and try some tires with a bit more tread.

The bike might also feel a little less floppy with a slightly shorter stem and possibly wider bars. If you have the same reach as your road bike it sounds like you could go a little shorter on the bars and you would have a little less leverage over the front end.
 

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Mike T. said:
Oh don't worry; I'll keep ye updated alright. With having two nightmarish long trail bikes in the past (Kestrel & Bontrager) and hating them and knowing what a steep HA mountain bike feels like (my 72 degree Seven) I'm on a bit of a mission with this new frame. I just can't see where the vagueness is coming from though.

If I could lay my hands on a cheapo 1.125" steerer steel CX fork I'd bend that thing to give me a bit more rake (and less trail) to see how that would feel. Maybe I'll take a look on e-bay.

Have a look at my bike here Walt to see if the geom looks normal to you. I can send a pic with it on hard ground if that will help.
Mike, I would put some different tires on it, maybe slicks, and see how it feels on hard surfaces.
 

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Discussion Starter · #15 ·
shiggy said:
Mike, I would put some different tires on it, maybe slicks, and see how it feels on hard surfaces.
What I'm gonna do is to put some Michelin ProRace 25's on my road bike tomorrow and go for a spin. Then for the next day I'll put those same tires on the cyclocross bike and do the same route. Then I'll know the handling differences between the two bikes. With those 25's I can do my "normal" type ride - some trails, dirt & paved roads.

I wish I could compare with my main bike for the past many years - my mountain bike with 72 degree head angle and rigid carbon fork. There was none of the handling issues with it that I'm feeling with the new CX bike. That bike steers like a laser. I would have liked to have measured its trail too.

But I can't compare as a month ago I t-boned a loose dog on a trail (damn f*&^%$ walkers of loose dogs) and the fork is busted in half (my face almost was too).
 

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I had a bike a few years back that exhibited some of the traits you mention. It was a cyclocross/touring bike, with a nominal 72 degree head angle, 50mm offset. I rode it with a fork with about 10mm shorter AC than specc'd and 52mm offset, which near as I can figure lead to a head angle of 72.6 and trail of 53. Not high trail.

What I noticed was that the bike didn't like transitions between pavement and dirt. The front end would tend to "tuck in" at the transition point from pavement to dirt. It would also wash out on gravel turns. I have used the same tires from that bike on other bikes without these problems, so I could rule out the tires. It also didn't feel quite as good in corners as other bikes I've had, diving in a bit rather than smoothly radiussing the turns. That could be unrelated to the "tucking in."

I'm not 100% convinced the washing out and tucking in was a trail issue. I have ridden very high-trail bikes, for instance an old non-suspension corrected Trek 990 with Rock Shox RS-1. That bike wandered on slow-speed climbs, and was hard to knock off line on fast downhills. That was to be expected from very high trail. But it didn't wash, that I can recall, or it did, at least not suddenly like the cyclo/touring bike.

I've also had bikes trail figures in sixties and seventies. My road bike (with 32mm actual tires) has around 61mm of trail; and my 29er has around 73mm of trail (72.5 head angle, 39mm offset), and neither of those washes out like that cyclo/touring bike I had did. One thing that was a bit odd about the set up of that cyclo/touring bike is that I was using a longer stem on a somewhat shorter top tube, that combined with the long chainstays probably tended to put more weight on the front. Could that have been the issue? I have no idea. But what you might try is a shorter stem and sliding the seat back, at least as a diagnostic to see if that changes the problem at all. I have a hunch might be more about weight distribution than steering geometry.
 

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Discussion Starter · #17 ·
John_Biker said:
...........what you might try is a shorter stem and sliding the seat back, at least as a diagnostic to see if that changes the problem at all. I have a hunch might be more about weight distribution than steering geometry.
I read all your interesting observations John. The stem (100mm) and seat set-back are the same as on my road bike and that has none of the characteristics of my CX bike. The only real difference, apart from the 72HA and longer trail, is the bars are slightly higher and further back which is not a bad attribute for a CX bike versus a road bike.

Yesterday I rode my road bike (carbon Argon18 Platinum) on a 30-mile trail-paved-dirt combo ride which is my normal CX bike stuff. I chucked on a set of 25mm tires to take the stones better on the dirt roads. I intend to repeat that ride on the CX bike tomorrow with those same 25mm tires.

The main issue I'm having with the CX is low speed wander which is worse when chugging up a hill. It's rock steady at high speeds. This, to me, points to a long trail issue. I didn't get that yesterday with the road bike.

When I've done the tire-swap test on the CX bike and have collected my findings I could try flipping the stem to lower the bars to my roadie position. Maybe this will put some more weight over the front wheel. But..........one change at once.
 

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Discussion Starter · #18 ·
Here's my follow-up to that post. Today was the re-test - the CX bike was outfitted with the same tires (Mich ProRace 25mm @ 90psi) as I had on my road bike two days ago. I did the same route (trail-paved-dirt combo) and my sensitivity meter was pinging.

Observations - The CX bike was slightly more vague (wandery) at sub 20mph speeds. Over 20mph the CX is rock-solid steering. Paved road or dirt road - same. Smooth narrow tires aren't good for sandtraps and gritty corners. Only my natural athletic ability (aka "sh!t luck") saved my arse.
I think the CX bike is more "wandery" with the Challenge Grifo Dry 32mm's (50psi) than with the ProRace tires. I'll bet the bigger, softer CX tires produce more Trail.

It feels to me that the bike has a tight headset but I know it doesn't. I personally am putting it down to the longer trail (approx 67-70mm, home-measured versus approx 50mm of the road bike) and my sensitivity to it. I've had two long trail mountain bikes before (Kestrel CSX and Bontrager SL) and didn't like them at all. A 72 degree head angled custom frame (Seven) cured that problem.

Sigh..........I just don't know what I'm gonna do this time around. Maybe I'll just frikkin' ride.
 

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Time for a custom fork?

Maybe something around 55mm rake would do you.

Your "just suck it up and ride" idea isn't bad either, though, and it's free.

-Walt

Mike T. said:
Here's my follow-up to that post. Today was the re-test - the CX bike was outfitted with the same tires (Mich ProRace 25mm @ 90psi) as I had on my road bike two days ago. I did the same route (trail-paved-dirt combo) and my sensitivity meter was pinging.

Observations - The CX bike was slightly more vague (wandery) at sub 20mph speeds. Over 20mph the CX is rock-solid steering. Paved road or dirt road - same. Smooth narrow tires aren't good for sandtraps and gritty corners. Only my natural athletic ability (aka "sh!t luck") saved my arse.
I think the CX bike is more "wandery" with the Challenge Grifo Dry 32mm's (50psi) than with the ProRace tires. I'll bet the bigger, softer CX tires produce more Trail.

It feels to me that the bike has a tight headset but I know it doesn't. I personally am putting it down to the longer trail (approx 67-70mm, home-measured versus approx 50mm of the road bike) and my sensitivity to it. I've had two long trail mountain bikes before (Kestrel CSX and Bontrager SL) and didn't like them at all. A 72 degree head angled custom frame (Seven) cured that problem.

Sigh..........I just don't know what I'm gonna do this time around. Maybe I'll just frikkin' ride.
 

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Discussion Starter · #20 ·
Walt said:
Time for a custom fork? Maybe something around 55mm rake would do you.
Ya know Walt, just before I did my last post I was using Mrs T as a sounding board (she's a good listener) and bouncing all my options off her. The "custom fork" was one of them as was another frame with a steeper head angle (that one's way less likely). But I'm also smart enough to also ask her "But what makes ME so special that I take umbrage at the CX standard of 72HA and normal carbon CX forks?" She, as usual, did one of these - :rolleyes:

Your "just suck it up and ride" idea isn't bad either, though, and it's free.
That's prolly best. If I under-think and over-ride this issue it just might go away.
 
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