Question with indoor trainers...rollers
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Question with indoor trainers...rollers
Post by thumbies on Dec 7, 2007, 3:40pm
I am having a problem with my rollers. Normally I wouldn't post this on a MTBing forum but i have googled the problem and have strangely come up bupkis. Owing to the recent shoulder injury (which BTW is feeling much better), i NEED to have these things work.
This is the kind of indoor trainer that has 3 rolling-pin sized rollers mounted in a frame such that your back wheel is cradled by 2 and your front wheel sits directly over the top of the 3rd. A belt connects the middle roller to the front one so the front wheel spins when you are pedaling.
Everything works fine when in the saddle but whenever i get out of the saddle, the front wheel gradually slows down and will even come to a complete stop (after about 15 seconds) which drastically affects balance
as soon as i sit back in the saddle the front wheel resumes spinning
This problem has been getting progressively worse over the last few years. There is some 'glazing' on the rollers...they are PVC. It seems to get worse at lower tire pressures. There is no additional noise associated with the 'slipping'.
I cannot figure out what is slipping or what is causing the slipping. I can't for the life of my figure out what could be slipping so dramatically that would cause the front wheel to come to a complete stop....
There's really only 3 possibilities:
1. rear wheel is slipping on the middle roller
2. the belt is slipping on one, the other or both middle and front rollers
3. the front tire is slipping on the front roller
1- i guess this is possible, getting out of the saddle definitely shifts the weight forward, it also tends to make the poser transfer less constant
2- I have tried holding one roller fixed and making the other roller slip inside the belt and i cannot do it. Granted, i dont have a 35 cm lever (radius of wheel)
3. This makes no sense, unless more pressure on the front wheel somehow causes slipping
My next plan of action was to try to clean both the rollers surfaces, the pulleys and the belt tself with some sort of solvent. Have to be careful here though (for example: acetone will melt PVC). If that doesnt work, i was going to try making the belt more grippy (hairspray, belt dressing, pine tar)?
any thoughts?
Re: Question with indoor trainers...rollers
Post by g on Dec 7, 2007, 4:11pm
Is your front wheel centered over the roller?
All new rollers suggest that the front wheel should be directly centered on the front roller.
Could be the belt too. They stretch over time. If it's stretched, and then you increase the load on the front roller, I can see how it would slow down.
What brand of rollers are they?
-G
Re: Question with indoor trainers...rollers
Post by thumbies on Dec 7, 2007, 4:18pm
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If anything, the front hub is slightly behind the front roller...some people suggest that you put the front roller up to 3/4" in front of the front wheel's hub. I think at some point in the past i actually moved the front roller forward a bit...to compensate for belt stretching
i too, could see the additional load slowing down the front wheel, but enough to make the d**n thing come to a complete stop
They are OGC branded rollers...pretty generic. I paid about 150$ for them (new) about 15 years ago. They are non-folding so the belt remains in tension all the time. I have tried getting a replacement belt before but all that i found locally was a belt that was much larger in thickness (mine is about 1/4") and i presume that there are different belt circumferences available since there are several different drum diameters on the market (from 1.5" up to 4") this would be a significant change in total circumference i think.
belts for rollers is not something that are usually 'in stock' in a local bike shop...
hmmm....D
Re: Question with indoor trainers...rollers
Post by stoner on Dec 7, 2007, 8:06pm
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It's the belt slipping, I think.
My rollers had the same problem a few years ago, and it too was worse when the tire pressure was lower. I tightened up the belt and it was fine.
I don't think that the rear wheel is going to slip on the roller or that the front is going to slip either. A stretching belt and reduces the amount of torque that the belt can transmit to the rollers and when the tire pressure is low and you weight the front there is more rolling resistance. BTW, when you do this experiment when the front wheel stops see if you can see if the belt is still going. You obviously can't tighten the belt anymore?
Hairspray is maybe a good idea. I don't know what else to suggest.
Glad to hear the shoulders better, boy.
P.
Re: Question with indoor trainers...rollers
Post by g on Dec 8, 2007, 10:46am
I have roller belts. In stock.
-G
Re: Question with indoor trainers...rollers
Post by thumbies on Dec 8, 2007, 7:27pm
So it was the belt slipping, not surprising really....
what i did to fix:
Pine tar...comes in a little spray bottle, its meant for baseball bats. Its awfully sticky stuff, i guess it improves the grip of the bat on the ball. I used to put it on my rims of my trials bike...modulation sucked but you could lock your wheels with even crappy brakes (canti's...heck probably even U-brakes).
Anyway, after applying this pine tar spray to both the front and the middle pulleys the problem was drastically reduced. Now there's a high pitched squeal (from the belt slipping) whenever i'm not pedaling smoothly (like standing)...its kind of annoying but a real encouragement to smooth spinning.
I wonder how long the tar will last?
Glenn, I'll prolly come in Tue. morning with my rollers to see what you have for belts.
thanks, Dave
Re: Question with indoor trainers...rollers
Post by g on Dec 9, 2007, 4:05pm
Sounds good Dave, glad you fount the culprit.
-G