[noysboy]

OK, im a newbie to tubulars. I watched and read articles on how to glue and I thought I did a decent job. However, on my first ride there was a recurring bump. The only thing I can think of is that I used too much glue and it clumped up, causing things to be unbalanced. Does that sound familiar to anyone? I assume the only way to fix is to remove the tire (!) and remove the glue from the rim and start over. How screwed am I?

I think I'll contact my LBS and see if they can help me out...but I'd like advice/opinions if you have them.

 

[Fireform]

More likely you didn't get the tire on perfectly straight. Could you just spin the wheel and look at how the tire moves?

 

[noysboy]

I *think* they are perfectly straight...but ill recheck tonight.

More likely you didn't get the tire on perfectly straight. Could you just spin the wheel and look at how the tire moves?

 

[Daren]

What tire did you use? I have noticed certain Continental tubulars av a bump no matter how meticulously you are with seating them

 

[noysboy]

They are continental sprinters

 

[wetpaint]

It is at the valve stem? What pressure are you running?

 

[cxwrench]

It is at the valve stem? What pressure are you running?

^ this ^ most likely. answer these 2 questions and i'll bet we find the problem.

 

[noysboy]

Hmm, Ill have to look more closely at where the bump is at. During slower riding, its not as noticeable. Pressure is 100 on rear and 95 on front.

It is at the valve stem? What pressure are you running?

 

[noysboy]

IF it is at the valve stem. What should I look at to fix?

 

[cxwrench]

IF it is at the valve stem. What should I look at to fix?

you might have to make the valve hole in the rim bed slightly larger to accomodate the bump.

 

[Kerry Irons]

you might have to make the valve hole in the rim bed slightly larger to accomodate the bump.

Or maybe the OP didn't put enough tension on the tire when mounting it and the tire is a little "bunched up" at the valve stem. IME the best way to get rid of that valve stem bump was to really lean on the tire (both directions) as you first started working it on the rim starting at the valve.

 

[JimP]

I think you are on to the real problem Kerry. If the tire is glued and not re-stretched it can be difficult to mount which can cause the bump at the valve. I put a thin layer of glue on the rim just prior to mounting so it is easier to get it straight and without a bump.

 

[Salsa_Lover]

If the rim is a 50mm carbon one, it's probably the stem/extender weight

 

[simonaway427]

I run a 58mm clincher with an 80mm stem....no bumps.

 

[Kerry Irons]

If the rim is a 50mm carbon one, it's probably the stem/extender weight

Are you suggesting that the weight of the valve stem/extender is enough to cause a thumping that you can feel? In order for this to be true, the force of the out of balance wheel would have to be enough to compress a tire with 6-7 bar pressure. Not likely. You can feel out of round wheels/tires, but not out of balance ones.

 

[cxwrench]

If the rim is a 50mm carbon one, it's probably the stem/extender weight

oh really...? :shocked: what are you pulling this info out of?

 

[SwiftSolo]

The likely problem is the valve stem. Check to see if it the tire is completely seated around the stem. Tubular wheels often come with a too small hole for the base of the stem and it results is the tire not being entirely seated for a couple of inches on both sides of the stem.

I *think* they are perfectly straight...but ill recheck tonight.

 

[wirider]

Continental tubulars are notorious for lump and bump from the valve stem area. The solution is to slightly expand the valve hole as cxwrench posted. There is mention of this in at least wheel building book I have seen, and that referred to enlarging the hole on aluminum tubular rims carefully using a drill to slightly enlarge the hole and then dremel tool to radius/smooth the edge- be careful not to overdo it and weaken the rim too much, particularly on many of the older very narrow width tubular rims. The author of that wheelbuiding book was building wheels for pro 6 day riders and european road pros and world champion cross riders so I'd trust his techniques.