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K&K
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Discussion Starter · #1 ·
Our bike has gone nuts...

I think this is a wheel-building (dish) issue, so I'll probably go over to the wheel board, but thought I'd run it by here first.

Just got back from our first ride on a new wheel-set. I felt like I was on a track-bike, and not in a good way. The bike wanted to turn! Anything but straight ahead. A little left and it would pull left, a little right and it would pull right (but not as much). It was downright scary on the downhills. Climbing was better, but any maneuvering was still very strange. Like I was on ice.

Here are the particulars:

Rims - Replaced DT Swiss FR 6.1D with Mavic EX823. UST, slightly heavier, but only a few grams.

Tires - Replaced tubed WTB Mutano 2.4 (very light and flexible, flat profile) with UST Continental Trail King 2.4 (heavy [but no tube] and stiff, round profile and significantly bigger despite the specs to the contrary)

Don't have a dish tool. Checked rear dish by clearance between the stays after I mounted the tires (not much, so seems to be within 1/16"). On the front I used a calipers against a machinists square on the fork stanchions. Not terribly precise, maybe 1/8" error.... but no more than that.

Not a fun ride ... Anyone have any idea what's going on?
 

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K&K
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Discussion Starter · #3 ·
I have very little experience, though this is not my first build. I am of the opinion (perhaps wrongly) that the tighter the better. I work largely by pitch. Initial truing was done only tightening, which I did until I twisted a nipple off. I used that pitch as my maximum tension limit.

I can deflect a spoke at mid-point about a 1/4" with some effort.
 

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Tires

Tire shape can be a real blessing or curse depending upon the dirt.

Could be spokes but that just seems like the wheel would need to be super slack.

Before going to crazy, verify the tire pressures make sense for those tires and the dirt.

PK
 

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K&K
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Discussion Starter · #5 ·
All rock, loose on loose and gnarl. The gravely stuff was the worst. I ran them at 30psi. The previous tires where much less stiff and much less round and that seems a possible explanation but the difference was crazy. It's like it's a different bike, and I don't like it at all! I cut the ride short because I was so unnerved. Do you really think it could just be the tires?
 

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K&K
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Discussion Starter · #8 ·
NY, Yes. The whole point was to have a "real" UST wheel-set and tires. Have had great luck on the singles in this terrain when we switched over. My wife, at 130 lbs, runs 18 psi with no issues and great traction. I'm 215 and run at about 28 psi.

Pat, I was thinking that, but the old tires are not UST. I guess I could put them back on with tubes and see what it was like. I'm thinking of mounting some Nevegals, a similar tire to what we had been riding and the tire we run on our singles.

Went to tubeless to avoid snake-bites. I'm guessing higher pressure would make this worse. Already sliding around too much.
 

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Is this a new wheel set, or a new wheel set on a different bike? new fork or any other changes? just looking at other variables outside of the new wheels, haven't really heard of anything like you describe.
 

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NY, Yes. The whole point was to have a "real" UST wheel-set and tires. Have had great luck on the singles in this terrain when we switched over. My wife, at 130 lbs, runs 18 psi with no issues and great traction. I'm 215 and run at about 28 psi.

Pat, I was thinking that, but the old tires are not UST. I guess I could put them back on with tubes and see what it was like. I'm thinking of mounting some Nevegals, a similar tire to what we had been riding and the tire we run on our singles.

Went to tubeless to avoid snake-bites. I'm guessing higher pressure would make this worse. Already sliding around too much.
We run Nevegals tubeless on our Fandango, me 180, wife 100. The handling when we're down in the 30lb range is very sketchy. MUCH oversteer, just as you're describing. The example where this is most notable is when I let the front wheel on my Yamaha Riva moped get too low...it does exactly the same thing, only more pronounced, likely because of the small diameter wheel.

Put the pressure at 40 and try it. Better yet, try 45 just for giggles.

We had a slow leak in that front last week on a ride...couldn't get it to seal and I used 2 CO2's, inflating periodically to get through the ride. When it got too low, it was oversteering like crazy. I knew exactly when it was time to throw some more CO2 in there.

MR
 

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K&K
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Discussion Starter · #11 ·
Mark, it seems everyone agrees I've been running too little pressure. I'll give it a bump and see what happens. Jeff, new wheel-set that I built (so anything possible could be wrong with it :)) and new tires.

As for how it feels... If you ever redesigned bikes as a kid, it's like when you put took the raked fork from your banana bike and put it on upside down, bolted on a little wheel so it'll fit in the frame, held on with some vice-grips for a head-set, you know, like that feeling :D
 

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Most previous air pressure threads have shown results to generally be in the high-30s to low 40s range. I run 40 front and 35 rear, tubes, and get terrible wander when the front drops much below 35.

As an alternative test, can you mount your newly-built tandem wheels to a single bike and see how it goes? I also like the old-tires test, just to see what happens. Easier tests than dealing with redishing the wheel or somesuch.
 

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K&K
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Discussion Starter · #13 ·
snip... can you mount your newly-built tandem wheels to a single bike and see how it goes? I also like the old-tires test, just to see what happens. Easier tests than dealing with redishing the wheel or somesuch.
Blow'n like stink, too windy to ride today, which got me to thinking.... the wind has been blowing like bat-**** lately, and two days earlier, both my wife and I crashed (on our singles) because of the high winds. Maybe this is all just wind related?? I don't remember it being particularly windy, but maybe I just didn't notice...

Eyeballing the dish, it looks good. Tires are as close to exactly centered as my eyes can discern. I'm not sure why I latched onto that idea, probably just my insecurity in my ability to build a wheel well.

This tire (Continental Trail King) is REALLY stiff. At 30 lbs, it feels far less compliant than what we've been running, but I'm thinking of putting the Conti-King on the back of my single and putting the Kenda on the front of the tandem and giving that a go. Okayfine, I like the idea of putting the new wheel on the single, that's smart, but changing rubber sounds easier than changing brake discs so I think I'll go that route. I'll report back after we've had a chance to ride with the Nevegal mounted on the new rim up front.

Thanks for all the input! Love this site :D
 

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Also, what are the respective widths of the old rim vs. the new rim? A narrower rim for a given tire size will have handling implications. Moreso if the new tire is even wider than the old.
 

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K&K
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Discussion Starter · #16 ·
No riding yet.... event at school keeping me busy. Will report back after the weekend...
 

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K&K
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Discussion Starter · #17 ·
Added pressure and had a terrible ride. Came "that close" to a crash when I turned into the upside of the trail and washed the front end out. Stoker is still nursing bruised ribs from that crash on her solo last week and a slide down the downhill side would not have be fun. My confidence is pretty much in tatters at this point which is of course, making me a danger to my wife. Sure hope I get this worked out soon.

Was reviewing all the obvious considerations when I noticed that I mounted the tire in the wrong direction! Hopefully it's that simple.
 

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Hopefully, but I doubt it. I've mounted directional tires backwards on the front and didn't experience this sort of change.

When you say you added pressure, what did you go from and what did you go to? Any other experiments (change back to old tires, swap rims to a single)? Rim width comparo?
 

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K&K
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Discussion Starter · #19 ·
Tread orientation - Yeah, I'm thinking that probably isn't it either.

The old tires are not tubeless. If I run out of ideas, I will put them on with the tube, but I think that will be my last option.

Pressure - I was running a bit over 30, went to a bit over 40. Very counter-intuitive to me because the front already felt "hard" to me, with far less traction than I am accustomed to, but enough people suggested it when I asked for advice, I figured I'd take it :)

So, I had established the dish by measuring from the fork to the rim, but there is no consistent reference spot to do that. Today, I made some wood feeler gauges and used the tire and the narrowest spot between tire and fork as my reference point. This worked quite well; it was very clear that the rim was not centered. I added what turned out to be more than a full turn to the disc side to pull it over. That seems like a lot... Figured that if I was that far off on the front, I better check the back too; sure enough, that was just as far off.

So, I've corrected (I hope) the dish, remounted the tire in the correct orientation, and our next ride will be with the pressure back down where we usually ride. Should have a report to offer tomorrow.
 

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Stupid question...How accurate is your gage. We can tell you a pressure, but if your gage is wacked it could be grossly wrong.

PK
 
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