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Vibration when braking using Mavic HELIUM's,Help!(7 posts)

Vibration when braking using Mavic HELIUM's,Help!MTG^
Sep 11, 2001 10:35 AM
I just got a pair of Mavic Helium's and every time I brake specially at low speeds it vibrates bad.I've triple check already the headset,toe in a little bit the brakes(hard to do on ultegra and dura ace),clean the rim and brake pad surfaces.I also have a set of Rolf Vector's and they don't have this problem.And the Heliums does this on both my bikes,one with ultegra and the other with dura ace.I could see the fork move or flex back and forward looking at the hubs when braking as I ride.I'm really concerned on the stress it place on the crown race area when braking since one of my fork is an all carbon design,carbon even in the crown.Is this common to Helium's?Is there a problem with the rim surfaces(since it's very grabby)?Any help and suggestion is appreciated.
re: Vibration when braking using Mavic HELIUM's,Help!Samcat
Sep 11, 2001 11:00 AM
Have a pair and I love them; no problems what so ever...about a thousand miles on them in the last10 weeks. No adjustments to the hubs or truing has been necessary, so far.

Questions:

Does the vibration occur in just the front wheel? Both?
Have you looked at how they set in the dropouts? Do the hubs need adjustment...are the wheels true? Do they spin smoothly when the bike is in a workstand? Have you checked the welded seam for roughness? Have you overtightened the QR and compressed the hub bearings?

Also, what do you mean about "grabby rim surfaces" The rim is basically a lightened out Open Pro...no magic there...just less aluminum in the sidewall.

If the fix doesn't seem obvious, get yourself back to where you purchased them...the wheels should be a delight...mine really are.

Sam
Reply for Samcat from MTG^MTG^
Sep 12, 2001 10:56 AM
Thanks for the reply.The vibration occurs on both front and back,but the front is worse.They set fine in the dropouts and the wheels are true,I have check them and they are new.They also spin smoothly on the workstand and the welded seams are fine.I did overtightened the QR tough on the first ride,but right now the wheels spin freely and there is no side to side play.How does overtightining the QR cause this problem?Any other suggestion?Thanks.
clean and toe inDog
Sep 12, 2001 5:26 AM
Could be a couple of things.

First, clean the rim. Get some automotive brake cleaner and clean the brake surface.

Second, remove your brake pads, and rub them a minute or so on some medium grit sandpaper. They might be glazed.

Third, put some toe-in in the brakes. You may have had it originally, but pad wear may have removed it. Should be able to swivel the pads a bit to get the toe-in. I do it by placing something between the pad and the rim in the rear, about .5 mm thick, and then clamp down the brakes while tightening the pad nuts.

Among those things, that should fix it.

Dog
clean and toe incyclequip
Sep 12, 2001 6:19 AM
I agree with Dog. As an addendum -IF you got 2nd hand Heliums you might need to remove the patina on the rim with a fine grindstone. Just rub the stone gently around the rim to get rid of any roughness. Also Shimano pads like to pick up grit which embeds in the pad causing the grinding.
For DOG and cyclequip from MTG^MTG^
Sep 12, 2001 11:03 AM
Thanks for the reply.I did all those things already and I still have the problem.I bought the wheelset new.What's a patina on the rim?Should I sand down the rim to make it smoother?Any other suggestion?Thanks.
moreDog
Sep 12, 2001 11:38 AM
If it were me, I'd next try new brake pads. Potentially cheap solution.

I'd make sure all the bolts on the brakes are tight, not allowing them to vibrate while braking.

Make sure the headset it tight, too, for the same reason.

You might remove the tires and lightly sand the rim braking surface with a very fine grit sandpaper.

If the wheels have had the spokes over tensioned, you may notice the rim wavering from side to side at each spoke. That could cause some pulsing. If it's that noticeable, I'd replace the rims.

Dog