Mountain Bike Reviews Forum banner
1 - 20 of 22 Posts

·
Your retarded
Joined
·
3,085 Posts
Discussion Starter · #1 ·
I'm not exactly sure if this is the best place to post this, but considering that this bike is intended to meet an AM/FR niche for me, it felt appropriate. I am having Dobermann Bikes build me a custom 4130 steel hardtail. I'm 6'4" with a long torso and weigh in at about 200 lbs with gear. I need a burly bike with geometry for technical, steep descents with pedals to the top. The frame will be setup with a 50mm stem, hi-rise bars, and a 2006 Travis Single 150. I think I have the geometry pretty close to what I want, but I could use some help with the bottom bracket drop and chainstay length.

What would a 0.75" BB drop put my total BB height with 26" wheels and 2.5 tires? Is 0.75" too little drop? Too much?

I'm thinking about changing the average chainstay length to 17.075" +/- 0.425". That would give me an adjustable chainstay length between 16.65" and 17.5". That would shorten my current length up by 0.425" which sounds better than what I have now.

<img src="https://i66.photobucket.com/albums/h257/nicklepics/Bikes/NicholasCustom-04-25-2007.jpg">
 

·
Registered
Joined
·
9,467 Posts
I'll bite. FWIW I rode a dekerf implant for a few years, and have some experience with geometry from working at a custom frame shop.

I am not used to calculating BB height based off of BB drop, but by my math, your BB is going to be around 14.5" with 2.5 tires. Thats pretty high for a FR/AM hardtail. I could be wrong though- definitely worth double-checking with the builder! I would shoot for a 13" BB, maybe even lower if you are prepared to trade some clearance for a lower center of gravity. I would weigh your trail preferences here- do you ride slow rocky tech stuff with lots of technical climbing, where a higher BB woudl help? Or, do you ride smoother, fast & flowy stuff, with jumps and berms- then go lower.

As for chainstays- one thing I have learned is shorter chainstays are NOT always better for climbing. Shorter means more of a rearward weight balance, which makes the front end lighter, thus you have to either shorten your fork or lean way over the front end to keep it down on climbs. My FR bike has long stays, and despite being slack it's very well-mannered on fire road climbs. If you have adjustable travel, then you're set. Otherwise, I'd vote for longer stays and make sure you get some tire clearance back with the extra length. 16.5" chainstays usually means 2.3" max tire size, unless the builder is using some tricks (like the evil soveriegn- very nice!)

If you're mainly doing urban, ignore my comments, everything I know is based off of trail riding and free-ride.

Looks like a sweet bike, keep us posted!
 

·
Your retarded
Joined
·
3,085 Posts
Discussion Starter · #3 ·
FM, that was a good reply. Pretty much exactly the feedback I was hoping to receive. This is my first custom HT (and really first trail HT in 8 years) so I am very unfamiliar with the specifics. I know what I want for the most part, it's just the little things that are holding me up.

I'm definitely a technical rider. Slow, rocky descents and climbs are the norm. However, I already have a bike built up for that task and am thinking that I should run a lower BB height as to make this one more all terrain capable. Looking at other AM/FR HT's, your 13" suggestion sounds about right. I'm thinking 12.75" is even better for this bike. If that were the case, what BB drop would I need? It looks like you are using a wheel + tire radius of 15.25". That sounds a bit high, but if that is correct, it would put my BB drop at 2.5". Hmmm... that sounds like it's a bit too much drop. Is the wheel + tire radius closer to 14.5"? That would put the BB drop at 1.75" which still sounds a bit extreme. (I suppose I'll have to measure my wheel + tire radius when I get home.)

Yep, I think the adjustable chainstays are going to be between 16.65" and 17.5". DWF had recommended the same and after some investigating, I think that's the way to go.

Let me get this BB drop thing squared away and I'll alter my drawing to reflect it. Regardless, I'll let you know how it all turns out.
 

·
Ride Everything
Joined
·
2,913 Posts
Nick,

Do you have the wheels/tires that you'll primarily use? If so, measure from the ground to the axle, and then subtract the BB drop, which will give you the BB height.
 

·
Your retarded
Joined
·
3,085 Posts
Discussion Starter · #5 ·
MileHighMark said:
Nick,

Do you have the wheels/tires that you'll primarily use? If so, measure from the ground to the axle, and then subtract the BB drop, which will give you the BB height.
Correct. Like most of my forum access, I only do it at work. I was planning on doing exactly what you recommended when I got home.
 

·
Your retarded
Joined
·
3,085 Posts
Discussion Starter · #6 ·
It looks like it is 14.5" from the ground to the center of a wheel and 2.5" tire combo. I'll use that number to tweak what I have.
 

·
Te mortuo heres tibi sim?
Joined
·
8,847 Posts
Nickle said:
It looks like it is 14.5" from the ground to the center of a wheel and 2.5" tire combo. I'll use that number to tweak what I have.
The drawing looks pretty good. Any sort of ETA, once you get the details final?

FWIW, the Peyto frame of mine that you got to spin around on has about a 12.5" BB height, and 16.5" chainstays. That's with the Pike, crown to axle of 518mm. TT of 22" and seat tube of 15.5" center to top. Not that that'll help you to much, but another frame of reference from a bike you've actually gotten to pedal around can't hurt.

I'd for sure stick with the shorter chainstay options, so long as Doberman can assure you of large tire clearance. Even with my short-ish stays, the Peyto has fit a 2.7" Intense DH with a bit of room to spare. Granted the chain would rub the side knobs when in the granny, but the only times I've run that large a rear tire on it were places the granny wasn't getting used anyhow.

Other thoughts that I like that may be totally useless to you:

*housing guides that let you run full for the shifting. it really is nice.
*slot on the seat tube forward facing, so less crap gets into the seattube.
*downtube bottle cage mounts. even if you think you'll never use them, nice to have for when you decide to take it on some long high country epic slog when a bottle might be nice to have. and battery holding for night riding.
 

·
Your retarded
Joined
·
3,085 Posts
Discussion Starter · #8 ·
scrublover said:
Any sort of ETA, once you get the details final?
Alain said 4-8 weeks. Like anything custom made, I would imagine that it will arrive at the end of that period.

scrublover said:
FWIW, the Peyto frame of mine that you got to spin around on has about a 12.5" BB height, and 16.5" chainstays. That's with the Pike, crown to axle of 518mm. TT of 22" and seat tube of 15.5" center to top. Not that that'll help you to much, but another frame of reference from a bike you've actually gotten to pedal around can't hurt.
Actually, that does help. It confirmed the geometry points that I want to see with this one.

scrublover said:
Other thoughts that I like that may be totally useless to you:

*housing guides that let you run full for the shifting. it really is nice.
*slot on the seat tube forward facing, so less crap gets into the seattube.
*downtube bottle cage mounts. even if you think you'll never use them, nice to have for when you decide to take it on some long high country epic slog when a bottle might be nice to have. and battery holding for night riding.
Good call, Scrubby. I added the slot suggestion into the drawing notes. The bottle cage mounts and housing suggestions are good ones, but I'll have to speak with Alain about whether or not they are possible.
 

·
Your retarded
Joined
·
3,085 Posts
Discussion Starter · #9 ·
Mathieu at Dobermann recommended that the SA be raked out more so that it is closer to the HA. He said the 4° difference would make my cockpit feel cramped and would force my knees into the bars when the seat is lower. I think he has a good point. The new SA will be either 69° or 70°.
 

·
Ride Everything
Joined
·
2,913 Posts
Nickle said:
Mathieu at Dobermann recommended that the SA be raked out more so that it is closer to the HA. He said the 4° difference would make my cockpit feel cramped and would force my knees into the bars when the seat is lower. I think he has a good point. The new SA will be either 69° or 70°.
Nick, the angles on my Kona are close to 70 parallel (despite what Kona claims), and it's gives a very "balanced" feel. I think Mat's suggestion of bringing them closer is definitely good advice. Something else to consider is your saddle's position relative to the cranks. I tend to keep mine well back for (seated) climbing, so the relatively slack seat angle on the Kona works in my favor (since I don't have all of the rails "hanging out"). Basically seat position will affect the effective top tube length.
 

·
Bodhisattva
Joined
·
10,833 Posts
Nick,
After riding with you the other day I have to really recommend that you consider a 29er HT.
The only two disadvantages as I see it are slightly flexier wheels (although minimal if you do I-9s again) and lack of a good long travel fork. Having said that, I thrash my 29er HT with Reba fork on stuff far more technical than what we rode the other day.

Give it some thought.
 

·
Your retarded
Joined
·
3,085 Posts
Discussion Starter · #12 ·
It's a tempting thought, but you are right, Squeaky. There are not many fork options that are up to par with the purpose this bike is being built for. This HT will be built around 26" round things that will take a beating that only my Preston receives. However, I would very much like to have a 29er for the future, and if I do, that will be built for more modest, longer distance trail riding.
 

·
Oh, So Interesting!
Joined
·
5,388 Posts
Nickle said:
It's a tempting thought, but you are right, Squeaky. There are not many fork options that are up to par with the purpose this bike is being built for. This HT will be built around 26" round things that will take a beating that only my Preston receives. However, I would very much like to have a 29er for the future, and if I do, that will be built for more modest, longer distance trail riding.
there is this (the new '07 fork is 135mm):

http://www.whitebrotherscycling.com/product-bw.php?specs=fluid29130

I'm thinking one of those forks on an Intense 5.5 29er, or a Spider29 w/Reba next year.

If you haven't been on a ht 29er, give it a try, its sooo much smoother than a 26" ht, I couldn't believe there was no suspension back there. Other disadvantages are that it'll be harder to manual and bunny hop, maybe worth the trade off depending on what you want it for. Either way, it looks like you'll end up with a nice ride, I'm jealous... and stuck pedaling my big pig around ;)
 

·
Bodhisattva
Joined
·
10,833 Posts
Nickle said:
It's a tempting thought, but you are right, Squeaky. There are not many fork options that are up to par with the purpose this bike is being built for. This HT will be built around 26" round things that will take a beating that only my Preston receives. However, I would very much like to have a 29er for the future, and if I do, that will be built for more modest, longer distance trail riding.
Valid point.
Consider this however: you already have that sweet Preston FR. It's tailor made for your terrain and style. What does the HT with big fork provide that the Preston won't aside from some weight savings?

On the other hand, a 29er would give you something very different when the mood suits you.

By no means do I think you're making a mistake with the 26er HT. It'll be sweet. But when I add a bike to the quiver I aim for something which provides diversity and try to avoid overlap.

Food for thought.....
 

·
Your retarded
Joined
·
3,085 Posts
Discussion Starter · #15 ·
Update

This:


got tweeked a small amount (69 degree SA instead of 71) and now looks like this:
















This little puppy goes into the powercoat booth this afternoon. :D
 

·
Your retarded
Joined
·
3,085 Posts
Discussion Starter · #17 ·
tvrbob86 said:
Holy Chromoly! That looks incredible. Please tell me it's going to be clear.
Nope. Chromoly oxidizes much more quickly than aluminum. There's a risk that it can rust under the clear. The color it's going to be painted isn't clear... kind of.
 

·
Interlectchewal
Joined
·
1,170 Posts
Nickle said:
Nope. Chromoly oxidizes much more quickly than aluminum. There's a risk that it can rust under the clear. The color it's going to be painted isn't clear... kind of.
I'm sure it'll look great whatever color it is.

I have a Haro Nyquist R24 BMX cruiser that's clear-coated "raw." The top tube got scratched up a bit during shipping and now has cool looking squiqqly rust lines under the clear. Are clear-coated bikes more susceptible to that, or is it just that it's visible, whereas on a colored bike it wouldn't be? Anyone know?
 

·
Oh, So Interesting!
Joined
·
5,388 Posts
Clear powdercoat is made to go over colored pc... not as a stand alone coating.

Nick, looks like you'll have a nice ride. Any thoughts on build? Interested in hitting Keystone anytime soon?
 

·
Your retarded
Joined
·
3,085 Posts
Discussion Starter · #20 ·
davec113 said:
Any thoughts on build? Interested in hitting Keystone anytime soon?
Yes and yes. A build is being priced out as we speak. Keystone should be happening very soon. It's kind of dependent on my work and relationship schedule. As much as I love biking, I love a healthy relationship with my GF more. ;-)
 
1 - 20 of 22 Posts
Top