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Trouble with open pros, and wheelbuilding q(11 posts)
|Trouble with open pros, and wheelbuilding q||rwbadley|
Feb 16, 2003 2:16 PM
|I have a wheelset of record/op and am getting a bit of shuddering from the front fork using them. I switched the front wheel with a known good one and the shuddering went away.
I can not see any blemish or cause for this, and am thinking possibly the wheel may have been overtensioned at one time (I did not own these from new) causing the rim surface to become irregular. The rear wheel seems to have the similar shuddering character. This all seems odd, as the wheels look essentially new.
I am resigned to rebuilding these wheels and am considering using a new set of cxp33 rims, as I have had good luck with them in the past.
Does anybody know if I will need to use new spokes (from op to cxp) due to length considerations? Or should I just use new spokes anyway if I suspect they have been overtensioned?
Could these op rims have some other problem I am not seeing?
|re: Trouble with open pros, and wheelbuilding q||curlybike|
Feb 16, 2003 4:35 PM
|If you look carefully at the OP rims in the vicinity of the label, you will find the welded joint. The joint is fine at the machined part of the sidewall but they frequently leave a high part of the weld bead outside the machined area. The brake pad is usually larger than the sidewall and hits that part of the bead causing the shudder. Realign the pads or file down the bead.|
|re: Trouble with open pros, and wheelbuilding q||ibhim|
Feb 16, 2003 4:46 PM
|Absolutely use new spokes...even if same length. After spokes set they work with each other. When rebuilding, will probably mix trailing and leading during reassembly, and they are set differently, creating new stress points. Why invite broken spokes?
Also, while switched with "known good one" and went away were different tires on the "known good one" or did you remount the same tire on the other rim?
The reason I ask, I have chorus/OP that I personally built this winter. When I put cheap 700x25's that I use on bricks and pump to 115 ran sweet (at least on regular pavement portions of the ride). That was my shakeout 50 miler to recheck spokes and round/trueing. Then put Vred Tri-Comps 700-23's, pumped to 140 and don't know as though I would call it shuddering, but very harsh and strange sound from front end. Will experiment bringing pressure down...
|re: Trouble with open pros, and wheelbuilding q||rwbadley|
Feb 16, 2003 6:23 PM
|The shudder is not a tick tick of the rim joint, it is a definite rim irregularity. The wheel did the same with various tires. The other wheel used (the known good one) was using the same brand of tire.
Thanks for the input on spokes, I do think fresh spokes would be cheap insurance against failure.
Tires up to 140 would be pretty stiff. I have had good luck in the 110-120 range using conti 3000. I don't know about the tri-comps.
Feb 16, 2003 6:44 PM
|Shuddering under braking or shuddering at certain (or all) speeds? Did you check the hub to see if it's adjusted properly or worn or in need of grease? What kind of fork?|
|My omission, oops...||rwbadley|
Feb 16, 2003 8:45 PM
|The shuddering takes place while braking. High speed is worse than low speed. I was braking before setting in for a high speed corner and it was so bad I about crapped my shorts. Then I started to examine for the cause.
The hub is adjusted well. The spoke tension is right. The fork is steel, but it happens on the carbon fork also with this wheel.
The spokes are 14ga. Picking the front up off the ground and spinning the wheel fast, I find with very light brake application I am able to feel the rim irregularity as a ripple in the brake pad/rim surface. I am not able to feel this ripple on the rim with finger pressure, and it does not appear damaged. I would also think it should show pad distinction on the braking surface if there were a problem, but I don't see that either.
I am surprised the OP rim has this problem. The rear shows the same trouble but it doesn't effect the handling like on the front.
Like I say, I guess I'll have to swap out the rims to solve the problem.
|odd and interesting||gtx|
Feb 16, 2003 8:58 PM
|I've never heard of overtensioning doing that sort of thing to a rim. Maybe cracking around the eyelets or even pulling through, but nothing that would mess with the braking surface. And you say this is something around the entire circumerfance of the wheel--not one spot like where the seam would be, something you could easily sand down. My guess is that there is a problem with Mavic's qc on these newer rims--something to do with the way they machine down the braking surface of the rim. But it's just a guess. Too bad you didn't have these from new. Maybe you could try a really abrasive brake pad, or put 'em on a cross bike and ride 'em in the rain and mud--a good way to brake in any braking surface! Good luck.|
|odd and interesting||curlybike|
Feb 17, 2003 8:48 AM
|Back in the days before they started machining the brake track, the entire rim was hard ano.. After many, many brake applications the rim would start to get wear spots on the ano.> Each spot would be directly at the spot where the nipple came through the rim and on the side that the spoke went toward at the hub, the opposite side of the rim remained ano..|
Feb 17, 2003 11:29 AM
|But I'm not sure that had anything to do with overtensioning--I always thought it had more to do with the process of manufacturing the rim. But who knows. It certainly was nothing I was conscious of braking. I have two sets of wheels built with MA40s and one set of GP4s (all these wheels were build by me). The anodizing is worn all the way off on the MA40s (doesn't take that long if you ride in the rain) but there is still some left on the GP4s which don't have as many miles (and it does have the wear pattern you mention, but it's not very pronounced). These old rims were a bit trickier to build with but I think they were more durable in the long run then the newer rims. Anyway...|
|Things to check||HillRepeater|
Feb 17, 2003 10:13 AM
|Check to make sure the hub/bearings are properly tensioned, as a loose hub could give a similar type problem. Also, check to make sure the brake track on the rim is clean - any oil or grease or other contaminant could cause a "pulse" during breaking. Finally, look to see if the rim is 'flared' along the brake track. This can happen when hitting road debris. The flared section of the rim would effectively increase the braking leverage at that spot, creating a pulse. You can correct any flares by carefully readjusting the rim with a cresent wrench.|
|Clean/roughen the brake pads too (nm)||Kerry|
Feb 17, 2003 5:49 PM