Belt Drive Transmission Issues - Trek District.

andyrr Posts: 1,822
edited December 2012 in Workshop
I've a belt-drive Trek District, supplied as warranty replacement for the previous chain drive version. Has been used for around 6 - 7 weeks or so. Works fine, as I understand it, the belt should NOT need any tension adjustment (in theory anyway) as being carbon-reinforced rubber it does not stretch to any degree but I had found that I did need to adjust (read increase) the tension via the sliding dropout adjustment screws a couple of times to eliminate a 'rubbing' type noise. Seemed to do the trick and my frame has the precise same dropouts as my chain frame but a few times I've suffered what I'd describe as a jump in the belt. Now, I believe that once that has happened the belt is compromised so needs replaced - I hope not as they are a lot more expensive than a chain - £5 for a SS chain, £35+ for a belt, gulp, belts supposed to be good for 10,000+ miles, I was replacing chains probably every 1,000 miles. at least they're a simple replacement.
Last few days I've had a vibrating/rubbing/sawing noise when putting most pressure on the pedals, eg climbing hills, of which there are many on my commute and last night I decided to increase the tension, having determined that, by guestimated hand measurement, the suggested belt slack of 2mm/0.5" with 5 - 10lbs force, was been exceeded on my bike's belt.
So I did this, maybe reduced the noise but part-way home I decided to stop and fiddle with the tension, the noise/vibration was just too much and I still had 10 miles to ride plus I was worried it could damage the transmission. A considerate motorbiker (Honda VFR750 ?) stopped and we chatted for a while - his familiarity with the transmission was explained by working at the Edinburgh branch of the Bike Co-op and he suggested I ensure the belt-line was good. Reducing the belt's slack tehre and then seemed to make the belt run just way too tight and the pedals needed quite significant force to rotate the belt so I backed it off again a bit. A few miles later, with now an accompanying metallic noise to go along with the belt noise I stopped again. All this in the cold and me in my sweaty state was not putting me in a great mood.
Examined the bike - the lockring on the rear sprocket was barely hand-tight ! I tightened best I could, played with the tension and eventually got home with the accompanying noise from the belt still evident, the lockring was still ok though.

In the garage with the wheel off, the lockring, outer retaining plate thing (black metal circle the stops the belt slipping off outwards) and then cog, could be removed by hand.
The freehub looks similar (not the same I think) to a std cassette freehub with what I'd term as splines running down the hub for the cog to slide down and for the retaining ring to do the same with the lockring engaging on the threads that are cut into these splines. I applied Coppaslip to the splines and reassambled then gave it a quick test ride - all seemed ok, transmission quiet but of course, about 1/2 way to work this morning the blooming rubbing noise returned, a brief check of the belt seems to indicate it's not tight enough so I'll be twiddling the tension bolts shortly to see if that sorts it out.

Now after the witterings above a few queries here :
Anyone else had similar issues with a) belt tension and b) rear cog loosening ?
Also I've seen that there is a special tool (like a chain-whip) for rear cog removal - seems I don't need this as mine comes apart quite easily ! However I'm not sure what tool is required to tighten the cog, this has around 10 indentations around the outer circumference that don't marry with any of my existing Shimano tools. Last night I just had to gently use big chisel and mallet to tighten the lockring but that's a bit of a brutal solution and as I was reasonably gentle I don't think it's as tight as I'd really like to get it.


  • nicklouse
    nicklouse Posts: 50,675
    sounds like the lock ring is not being tighten enough and this is causing the belt come out of alingment and rub.

    buy a lock ring tool.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • andyrr
    andyrr Posts: 1,822
    aye, I'd agree that certainly part of the issue has been as a result of the lockring becoming loose and allowing the belt to shift out of alignment but it should be fairly tight now so I'm guessing that the present noises are either poor alignment (due to incorrectly tensioning the 2 sides) or it being under-tensioned so allowing the belt to shift on the cogs.
    I'm just trying to work out what the correct tool is to tighten the lockring - if I can't source one in the next couple of days then I might get the supplying shop to check the transmission over for alignment and also tighten the lockring and if I do that and it runs ok I can have a go at home at determining/measuring the correct tension. I used a bent spoke and 6lbs weight to have a rough go last night but it's not the easiest thing to do with 1 pair of hands.
    Maybe like this one :
    Lezyne External BB and Cass Lockring Tool : ... elID=73442

    <edit to add>
    I've realised what the special tool is for - that is for holding the rear cog/pulley to enable the lockring to be loosened as using the belt is a no-no. Still not sussed what lockring tool is needed but I think it is not a particularly specific one so just a case of determining what one it IS .,,
  • Monty Dog
    Monty Dog Posts: 20,614
    Gates make a special tool to ensure the tension is adjusted correctly: ... egory=4081

    If the shop didn't do this correctly then trouble will likely follow.
    Make mine an Italian, with Campagnolo on the side..
  • andyrr
    andyrr Posts: 1,822
    I know the mechanic at the shop did originally spend time on the belt issue as we discussed this when I picked it up but whether they use a gauge or just do it manually I don't know. I'm now not sure if I have an issue with damaged belt and/or pulley(s) maybe as a result of the rear pulley running loose for a while. I'm wary of just setting each side to be same adjustment, via the sliding drop-outs, as I'm not sure if that will necessarily result in perfect alignment. I've made adjustments, sometimes to 1 side, sometimes both, ran higher and lower tension but now it just does not want to run quietly - tonight's return home had me stopping 4 or 5 times messing with the adjustment and once or twice I'd move off and have a nice quiet bike but a few minutes later as I had to press harder on the pedals the bloomin' noise returned and I'm left scratching my head.
    I'll have to see if the bike shop will take a look and hopefully it's just my ineptness as opposed to there being damage to the transmission - belts are expensive enough but having to replace either pulley would tip me over the edge.
  • andyrr
    andyrr Posts: 1,822
    I'm still suffering belt drive noises here - after returnign from the shop who set the tension and alignment I gave the bike a run up and down the road, doing some hard starts to see if the noise returned - nope, all quiet. Commute yesterday was also pretty quiet apart from the noise present right at the start and then it disappeared - strange. Then leaving work it almost immediately started and was alnost as bad as last week. I've searched around for help on how to setup the transmission - it isn't rocket science, but wonder if anyone has some good pointers ?
    Here : ... elt_ov.htm
    and the relevant adjustment method for me ... liding.htm
    they indicate that the idea, I think is to get the belt positioned correctly on the front and rear pulleys and then see if pedalling results in it wanting to move inwards or outwards. I'm about to try that but it really should not have shifted since the shop dealt with it - all bolts are tight, I've touched nothing in the meantime.

    Any belt-drive transmission people in the house ?