Play in SRAM Rear Mech

richie.bashford

Hi,

I have a Trek X-Caliber 8 with a SRAM X7 rear mech.

All is generally fine but it seems to be slipping every so often and ghost changing so figured its time for another cassette, rings and chain.

Took the wheel off and noticed there seems to be a fair bit of slack on the bolt connecting the derailleur to the hanger.

If tension is put on the cage to act as if the chain is there then it goes.

I've read that a lot of SRAM derailleurs have this play but doesnt seem right to me so thinking i may swap that as well.

due to shifters and ratio i assume i am stuck with SRAM so what is the best upgrade to the X7 and will this suffer from the slack issue on the mount bolt?

thanks

reaperactual

Is the bolt tight? Is the derailleur fairly new? All derailleurs have some amount of lateral play or movement if pressed which is normal.

You are only restricted to Sram if you want to keep the shifter.

steve_sordy

Ensure the bolt that connects the mech hanger to the frame is correctly tight. Also the bolt connecting the mech to the mech hanger. Several times in my biking career, I have had dodgy shifting, ghost shifting and so forth. None of my usual adjustments have worked. And then I noticed a loose bolt!

Check the simple things first.
Don't assume that your mech is worn out. I have never worn out a mech, not once. I have worn out jockey wheels, cassettes, chains, rings, cables and so forth, but never a mech (or a shifter)!

PS: Of there are no loose bolts, I would suspect the mech hanger alignment. If you look from directly behind the bike, the mech should hang vertically. If it doesn't then you will have all sorts of odd shifting problems. It should cost £10 (or close to it) for the bike shop to align the mech. The tool to do it costs between £35 - £55 depending upon whose brand you get.

richie.bashford

I checked the hanger all seems to be dead straight. Also looking on the forums here it seems to be common for these to be loose with some people changing the bolts to one's off the more expensive mechs and have found this will fix the problem. I also had an email back from sram who said they will wobble when not under tension....

So this now leads me onto my next issue.

I can't seem to find a replacement chain ring. Mine is truvativ 36/24 and where I've looked seem to be out and I like the ratio this gives so would like to stay with it.

Now my next route was shimano 36 but they all seem to want to be matched with 22 but would a 24 cause any issue?

If so is there any recommendations for online stores that don't sell Chinese copies.

steve_sordy

I would go with the Shimano 36/22. It will give you a 10% wider gear range and allow you to go up steeper hills. Do not fit a 24t in place of the 24t. The shifting ramps on the 36/22 will all be designed to complement each other as will the tooth orientation. If you fit a 24t, it will still work, but not as crisply and smoothly. I know becasue I have experienced something very similar.

For example, here are two Shimano 24T gears. One is designed for a 2x10, the other is designed for a 3x10. The teeth are not aligned! The one in the background is for the 2x10, the black one is for a 3x10! Who knew?

richie.bashford

I'm not sure why this is proving to be so hard.

My mission started because there was play and grinding in the rear hub again so decided to get a new axle and bearings and free hub whilst I was at it.

Then thought maybe a new cassette and chain was in order at the same time but where I can easily find everything else, finding these chain rings is becoming a tadd tedious.

I've managed to find a shimano 36 for 10 speed chain but now I can't find a 22 to go with it that is 10 speed and made for a double front setup. They're all 3

JBA

What chain set has the bike got?
I don't think you can fit a Shimano chainring to a Truvativ (SRAM) chainset as the offset is different.
What year is your X-Caliber?

richie.bashford

It's a 2016 but when I got it I had an issue that every ride I went on a spoke or two snapped so after many complaints trek gave me credit in a shop to have some wheels custom made.

So the new wheels have shimano hubs with a hg81 cassette. It has hg54 chain so that's why my thoughts are shimano chainring makes more sense. The sram rear mech has never had an issue with a shimano cassette and up until recently has been perfect.

I stretch chains pretty quickly but I do a fair amount of miles on it so this time thought whilst new chain may as well do the lot as I was on a mission with the rear axle.

JBA

What chain set?

richie.bashford

sram s800
2x10 36/24

Basically all I'm after is the rings that don't cost hundreds of pounds or come from a market in china via eBay.

Or a shimano pair that will fit on the sram arms.

I've looked at the shimano m617 which looks as if it may fit and if not I'm getting so bored of this now I'd just dremel the arms until they did.

richie.bashford

Hoping those photos added OK.

If so then it shows the gap in the current ring I'm hoping the shimano has as they seem way easier to get hold of and cheaper than sram when I come to doing this again next year.

Now I know why my local shop charged close to 200 sheets for the pleasure

JBA

A Shimano ring won't fit without a bit of grinding.
You can buy a Shimano Deore chainset complete with chain rings for £65 - £70. I'd just do that and save a load of hassle.

richie.bashford

Yeah I was thining a quick grind and we're done.

Or go for one of the many truvativ rings I can find that don't match mine and hope they work or go for the £70 sheet option along with the required hollow tech bearings

richie.bashford

Or if can find any truvativ 36 ring in the UK so I don't have to wait a month for it to arrive am I correct in thinking that as long as it has ramps and pins, is ten speed and 104mm bcd it will work?

steve_sordy

Sadly, I don't believe it is as simple as that! (See my post of 3rd June)

The ramps have to be in the correct place, as do the odd shaped teeth. They are both shaped and situated to facilitate smooth and fast shifting. Get them in the wrong place and it all goes Pete Tong!

All the manufacturers have their own ideas and of course they do not cooperate, because smooth and fast shifting is a marketing edge.

richie.bashford

Continuing my bike service my new axle and freehub arrived this morning.

So just fitting the freehub and thought I'd check the torque online expecting to find something like 30-50 but instead found this on a shimano pdf.




Surely 200 nm is a tadd excessive. Car axle bolts aren't that tight.

richie.bashford

Of course looking in the box has revealed the instructions with 35-50 printed on it

richie.bashford

Now another question for the experts...

Hub bearings.... I've seen some people who say no play what so ever and some who reckon a small amount when the wheel is off the bike is better as the quick release compresses the axle.

I'm not convinced the pressure of the quick release on the axle would compress it to shorten but that's what these websites are here to discuss I guess 😊

reaperactual

Correct. I left a little play and quick release does apply enough pressure to stop play.

Some try and pre load bearings out of the bike with quick release attached with various ways including clamping wheel on outside of one of the drop outs although I never bothered with any of these methods.

steve_sordy

200Nm!

That is 147 ftlbs. In other words, ten and a half stone on a one foot lever. More than a tad excessive! Shimano have opened themselves up to being sued for damage.

It has to be a typo.

richie.bashford

https://si.shimano.com/pdfs/dm/DM-MEHB001-00-ENG.pdf

Page 13

I just googled freehub torque and this appeared.

I hope no one followed these instructions.

JBA

You are reading the wrong document.
That 200Nm torque is correct for the type of free hub you have linked to: a screw-in trekking type.
However, for an MTB freehub such as Deore, SLX or XT it is 35-50Nm.
Page 18 HERE.

richie.bashford

Now here's a lovely story. Small ring arrived this morning so completed my service of my bike.

Went for a quick ride to test out and everything is smooth and working as should.

Then when just about to pull off the chain snapped. At first I thought it was the link pin but it was a factory join.

I'm hoping this is just bad luck as its the first chain I've known snap and I never change gears when applying pressure.

All I've done is change the chainset from 22-36 to 24-38 along with new cassette and chain.

Is this just a case of bad luck or will this small change make any difference?

steve_sordy

It could be just bad luck and its worth a warranty claim. But there may have been a set up problem.

Did you check the chain length before fitting? Your old chain may have been too short, but you got away with it. Adding two more gears to the front means you need a slightly longer chain. I know it was only two teeth, but it could have been the straw that broke the camel's back.

There is all sorts of stuff on the internet on setting your chain length. But don't forget to check the length with your rear suspension fully compressed as well. Many suspension designs extend the rear axle as they compress. This will put tension on the chain. You were lucky just to break the chain, I have hard of some riders getting their mech ripped clean off when they bottomed out the suspension.

richie.bashford

Now for my next bit of entertainment...

What can anyone tell me about chordal action on chains.

I've noticed that when in the two smallest cogs on the back there is a vibration/rattle/wobble of the chain. Its only noticeable as it tings against the front mech.

At first I thought it was the low stop screw adjustment on the derailleur but all seems right. No usual misalignment noaies.

All other gears are smooth and quiet.

Is there any magical solutions to this or is it something that affects all chained devices to a certain extent?

This is after new cassette, both front rings and chain so I was thining new jockey wheels may help

reaperactual

Chain noise on small cogs is probably because the chain is rubbing the front mech cage.

In my experience front mechs rub in extreme gears and I found it impossible to tune out.

Adding tension to front mech will stop it rubbing and move it out further but the consequences are poor down shifts if you go too far and vice versa.

Always seems impossible to get them working without compromise. On my previous 3x9 drivetrain I tried everything and was never able to stop chain rub on front mech cage in outer rear gears, one of the reasons that pushed me to a 1x drivetrain.

steve_sordy

I agree 100% with reaper. Because the side of the chain is neither flat or smooth, any contact with the front mech guide will cause vibration. Even if you could avoid that source of vibration, there is another source, which cannot be resolved.

Chain rings are not round, they are regular polygons. This is why chain drives are never smooth. The fewer teeth you have, the worse the action becomes. When I studied this stuff I was told that 9 teeth was right on the limit. Chain pitch does not affect this, it would be 9 teeth even if the chain pitch was half the size. I used to know how quickly the vibration dies away with increasing tooth numbers, but that is a memory long gone.

richie.bashford

It's not the adjustment on the front mech. The chain is perfectly centered and this is when the bike is upside down so I can spin it up so its not the force on the crank arm bending the ring out towards to the side of the front derailleur.

At slow speed the chain is flat and smooth but as the speed increases the vibration increases.

It's hard to explain but it's like the chain rattles from side to side slightly only in two smallest cogs.

I will try and add a video on here.

reaperactual

Turn the bike the right way round spin cranks in small/small combo and check for slack chain at the bottom and make sure the rear derailleur cage is still under tension. Chain could be one link too long?

richie.bashford

Yeah I did think of chain length but I've gone up 2 teeth on the front so if anything the chain is tighter than it once was and I never remember seeing this happen before.

I'll get a quick link and try a link or two shorter

JBA

If it only happens/you can only see it when the bike is upside down don't worry about it. You don't usually ride the bike that way up so it's nothing to worry about.