Looking for specialist MTB bike mechanic

[Sandro]

I'm at my wits end and about to give up on a second hand dual suspension I bought a few months ago. The bikes history is it fell off he back of a bike rack but not at high speed. The gears gave trouble after that, even snapped a few chains. I decided to buy it to fix up and use myself. I took the drivetrain off my hardtail and basically swopped the parts. The bike actually worked fine for a few months until it needed a service. I decided to take it in, I was told the chain needed replacing, the cassette needed replacing, the gear cable housing and the BB set as well. The parts were all supposedly replaced, even though I later realized they hadn't all been but lets leave that rant for now. The gears ended up being a disaster, the bike wouldn't even change onto big chain ring. I took it back and when I tested it the chain kept being thrown off the big chainring this time. I decided to take it elsewhere as I didn't even have the patience to go back there again. I took it to another shop that were at least a lot more helpful and made an effort to try fix the bike properly. They said they thought the problem may have been solved but they didn't even want to charge me until I was happy, they said the problem could have been the derailleur hangar was bent which made sense actually considering it's history. I paid them anyway because I appreciated their honesty. The gears were better but slipping on big chainring, I took it back and asked them to give it a proper major service which I was happy to pay for even though it had recently been 'serviced' . They changed the rear derailleur wheels and the gear cable housing as that hadn't been changed after all. The gears are however still slipping in big chainring, specifically under load. I don't really know what to do now but I can't keep throwing money and replacing parts as the whole process of elimination is getting a bit expensive especially considering its an old bike. Is there anyone who thinks they can sort out the problem, I'm at a stage now that I might just sell the bike as is, and disclose the trouble upfront and pick my battles rather? I would actually upgrade the whole drivertrain to a 1*11 or 12 but I definitely don't want to go to that expense if the problem persists. Appreciate any input you may have.

[Steady Spin]

During all the changing of chains etc did you ever replace the chainrings?

[AkwA]

If you not too far away, dont mind taking a look, free of charge ofc, could be a short chain, or worn chainrings as Spin suggests.

[Sandro]

10 minutes ago, Steady Spin said:

During all the changing of chains etc did you ever replace the chainrings?

They haven't been changed they did tell me they checked them though. For what that's worth anyway.

[porqui]

Has anyone checked the B screw on the rear derailleur - easily overlooked.

AND make absolutely sure that all the derailleur parts are also straight and that the hanger is on the same plane as the rim. (small things massive issues skop skiet en donner issues)

(If the arms on the derailleur are not straight you will have issues (not talking about the side plates))

Edited September 3, 2022 by porqui

[Barry]

26 minutes ago, Sandro said:

They haven't been changed they did tell me they checked them though. For what that's worth anyway.

Maybe upload a pic of the chainring's. Sounds like they could be worn and not meshing with new chain. 

[Sandro]

10 minutes ago, Barry said:

Maybe upload a pic of the chainring's. Sounds like they could be worn and not meshing with new chain. 

Ok cool. will do - thanks

[Barry]

Had a problem like this some time back. Only slipping in big chainring and small gear under load. Turned out to be worn ratchet's on the DT Swiss freehub.

[Shaheedalex]

More details please...Bike ? drivetrain ?

[OVERDRIVE]

I'll leave this to @Jewbacca

[Jewbacca]

10 hours ago, OVERDRIVE said:

I'll leave this to @Jewbacca

Without seeing, touching and inspecting, I'm Stevie Wonder reading sub titles.

 

[Psyrax]

A proper mechanic need to spend time with this bike and have a good look. And he needs to be a patient guy - not rushing to get to the next job. 

A bike that fell off a vehicle/rack, needs a frame allignment, linkage and basically everything checked. 

 

[madmarc]

Ooooooo I love these kind of problem bikes

Slipping on the chainring under load with a new chain fitted ? - Worn chainrings - incorrect chain length - B screw setting - correct size chain for what ever speed it is.

If its a cable issue - Change both the outer and inner cable - one does not simply change the outer.

Not changing onto the big ring - limit screw adjustment on FD - FD alignment if its a clamp on - Check the cage is not bent - cable tension 

Rear gears not changing like butter - RD hanger (You say is replaced) - limit screws adjustment - B screw adjustment - correct chain length - RD cage could be bent - RD could be damaged - Cassette mounted properly - cable tension.

Fixing these kind of issues is actually fairly simple, but like you say, finding a proper mechanic to do them for you is the challenge.

 

[DieselnDust]

2 hours ago, Jewbacca said:

Without seeing, touching and inspecting, I'm Stevie Wonder reading sub titles.

 

my thoughts exactly.

The major issue seems to be "slipping on the chainring"

Now in all my years of cycling I have never ever seen a chain slip on the big chainring. It my slip OFF the ring, It may skip on the chain ring,it may be noisy.

Slipping off the chainring:

This could be a bent crank. In light of the bikes history the spider of the crank could be bent and you will notice this as slight wobble. Combine this with wear and a poor chain line and cahin derailment is a likely event.

Skipping on the chain ring:

This could be due to excessive wobble (bent crank) or bent teeth on the chain ring.

It could also be that the chainring is not compatible with the chin fitted e.g. a 9speed chain ring with a 11speed chain. (uncommon but in the not to distant past people were combobulating all sorts of parts to convert their bikes to 1x drivetrains on the cheap.

But I'm just speculating to add to my post count and keep the conversation going on a boring windy sihhty weathered Sunday morning

In short, this tread are useless wiffout pitchas

 

[Meezo]

You came to the right place...

The forum's

👀

[OVERDRIVE]

4 hours ago, Jewbacca said:

Without seeing, touching and inspecting, I'm Stevie Wonder reading sub titles.