Wheel alignment problem

[Phillip]

Upon installing new Avid SD7 brakes today, I became aware of an alignment problem with the rear wheel on my '98 4000. The wheel is to the left off center.
Upon discovering this, I headed to my LBS where their Park dish check tool indicated the wheel is perfectly centered in relation to the XT hub. I installed  another wheel and got the same results off center results. What am I missing?  

[Matno]

What am I missing?  

Something besides your wheel is crooked.

Okay, that was a smart alec reply. For future reference, an easier way to double check your wheel alignment is to just flip the wheel around backwards. If it's off-center on the same side, then the problem is not your wheel.

As for your current problem, the carbon swingarm of the 4000 isn't prone to "bending" as far as I know. (I believe the carbon would show obvious signs of a crack, rip, break, etc). Thus, the other possibilities are that your pivot is off (could be loose, bent, or just really worn), your frame is bent (I think you'd be able to see that, but you don't mention exactly how big the discrepancy is, so it could be small), or your dropouts are asymmetrical (one or both could have come unbonded, gotten bent, or cracked. The other possibilities are that the swingarm has always been a bit tweaked and you never noticed it before (not likely) or you parked it next to something VERY hot and the swingarm warped (is that possible?)

Wow, that exhausts my creativity for the evening. Hopefully, one of those will be the answer, and hopefully, it will be one of them that has a simple solution (like a loose pivot). Good luck.

[Old Proflexer]

many were made 'to the left off center'

i have two that way (i've never built the third to check) and many here over the years have commented that their's is also.  i attribute it to a q.c. issue at manufacture (IMHO).  it would appear that either the left arm is a smidge too long or the right is a smidge too short - either way, many were smidged.



OP

[Phillip]

Thanks for the responses Matno and OP.

Using Matno's advice to turn the wheel around in the dropouts, along with a ruler,  I have discovered that the LBS was wrong and that there is indeed a 2mm offset.  

My questin now is; should I ride it as is or correct the dish? The wheel has been rebuilt and trued so many times I can't even remember. The 517 rim has even been replaced once. Other than the dish problem, it has a good "build". All the spokes are tight and the runout is true. Looking at the uneven brake arms bugs me though!  

[Simon]

Looking at the uneven brake arms bugs me though!  

I can't see any problem riding it as it is,however are you going to enjoy riding it knowing your brake arms are uneven ,re-dish it so your happy with it [smiley=nod.gif]

[kruhner]

I have a 98' proflex 4000 also with same problem.

I just pulled it over myself on the bike by loosening non drive side one turn then tightening drive side accordingly. I got it centred in the swingarm and now I am running maxxis mobster 2.7.  

[Carbon_Angus]

2mm is not that much, but a wheel should be dished properly to last and be efficient. what's wrong should be made right

your drops are probably not perfect either adding some to the situation. but i wouldn't mess with a minor problem there.

[smiley=beer.gif]

[Matno]

Looking at the uneven brake arms bugs me though!  

You could just move some of the washers on the brake arms so that the calipers look more even. They come with two different sized spacers, one on the inside and one on the outside of where the brake "shoe" attaches to the caliper arm. That way you can just swap the smaller one for the larger one to make minor adjustments. It can make a big difference in how your brake arms line up. Worth a shot. A 2mm difference in dish is not worth a lot of hassle (unless of course, it bugs you to no end). Of course, if you measured the difference between the tire position in both directions, then it could only be a 1mm offset...

[Phillip]

I started off using different spacers on each side, but it just didn't seem right. Thanks for the suggestion though.

The 2mm measurement was with a ruler between the swingarm and tire, viewed from directly above. The offset looks like a lot more than 2mm when viewing from the rear using the shock as reference. When I reversed the wheel in the dropouts, it was centered.

The one service that I have left to my LBS is wheel building and trueing. Maybe it's time to get a trueing stand and start doing it myself. Either way, my rim will be centered very soon.

Thanks for all the advice. What really got me scratching my head was when the LBS certified the dish as correct. Here is an example of why you should do all maintaince yourself.

[Matno]

Here is an example of why you should do all maintaince yourself.

Amen. Besides, wheel building is truly one of the (if not THE) most satisfying parts of bike maintenance. It can also be the most time-consuming and frustrating, but that's neither here nor there... I built my first set of wheels (on my road bike) last year and I'm happy to report that they are still perfectly true, quiet, and strong with virtually NO adjustment after the first couple of rides. Feels good!

Good luck.

[Irby]

My 756 had an "tweaked left" rear wheel. I used a shim made from a coke can to compensate. I cut a small piece and wrapped the left side axel threads with one layer. I had to replace it every so often. I understand that Pepsi cans will also work.

My "new" bike (1999 EVO) has the same problem. I uesed to corrected it by dishing the wheel. This produced a problematic wheel for me since the spokes were too tight on the right side. My current solution is to ignore it. The only thing is that it limits the rear tire size to 2.2. I can't mount my motoraptor 2.4 on the back now.

An idea that has not been mentioned is perhaps to try a Ritchey OCR wheel that you can "adjust" without having to have a huge tension imbalance between left and right spoke sets. Sorry to ramble. Hope you boys are getting out on your bikes. Dan

[Phillip]

The problem has been discovered. First of all, my LBS redished the wheel for free even though they didn't do the build. It was 1MM off.

What I discovered when I got the now perfect wheel back on the bike is that there is some slop between my XT axle and the drop outs. The wheel can be mounted true by adjusting it's position prior to clamping the skewer.  I see no sign of rounding out or wear in the area of the drop out where the axle fits in.

Has anyone else experienced this situation?

[Irby]

Philip, You are describing the same problem I did in my previous post. Try the shimming the axle with a bit of aluminum. If you wish, I can scan a diagram and send it to you. Dan

[Phillip]

Irby,
How did you keep the aluminum strip on the axel? Superglue? The srtip wants to unwrap prior to mounting.