BCDrums

Hi Bikers,

I am working on a shifting problem with my wife's beater bike, a 1990 Raleigh Assault mountain bike. It is correctly named, because it assaults its rider. But anyway...

It's a 3x6 Suntour drivetrain. It is 6sp indexed, and I haven't been able to get the rear to shift smoothly from low to high gear. The chain skips from 3 cog to 1 cog, and sometimes from 6 to 4 too. I changed the cable and housing, and thought that the shift lever was worn and skipping the gears, but that didn't solve the problem. It shifts correctly from high to low.

Now I wonder if the rear derailler spring might be worn out, or if it's the freewheel, which appears to be a 14-28. I could replace both, but am loathe to put any more money into this heap than I must. It's the bike my wife likes to ride when she's afraid it might be stolen. I should be so lucky.

The RD has a claw mount. If I need to replace the derailler, is it likely that I could mount a non-claw derailler onto the existing claw?

Thanks for your help.

Iride01 

You know the chain is not worn out? Some of the rear cogs might be worn out to.

If it's the DR spring, then maybe a good cleaning and lubing with something light will temporarily fix the issue and maybe show that is what the issue is. No other bike laying around you could do a temporary DR swap to see?

fietsbob

Much said is unseen.. pictures would be quite useful..

I've been using friction shifting on my 3 by 6 drive trains for 30+ years now ...





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BCDrums

I hadn't checked the chain, but I just did, chain is well worn. Cogs show some wear.

Will try cleaning the RD as you suggest. Cheapest fix first! I'd rather buy an inexpensive Tourney RD orsimilar than take apart a bike that's working for test, but a good suggestion.

BCDrums

Were it my bike, I'd be fine with friction, but the bride loves that click of an indexed shifter.

dsbrantjr

Attempt to isolate the issue. Try shifting by pulling on the exposed shift cable to see if the derailleur shifts smoothly. If it shifts OK start looking at the shifter and the cable coming off of it. If not, then try pushing the derailleur by hand (watch your fingers!). When you replaced the cable and housing did you replace the whole housing run, including the loop at the derailleur, which tends to accumulate rust and grit?

cpach

It sounds like claw might be bent. If its the kind with a normal derailleur mounting, it can be aligned with a hanger alignment tool.

70sSanO

IIRC, Suntour thumb shifters had a friction mode. But I doubt that is an issue as the shift lever would move if it is was slipping.

As with others, chain, cogs, RD could be the culprit. Shifting from high to low is done by pulling the cable, low to high is done by RD spring. With a new cable and housing, there should not be any binding, but you might want to make sure it is sliding freely.

John

dedhed

Suntour Technical Bulletin #21 "Accushift Problem Solving" in 31 Pages

fietsbob

Time to Buy new components then , new rear wheel build too.( all spare parts are old too..)
cassette freehubs are where the action is , now..
IGH are even easier to use all the gear ratio sequences are in a row.

Maeda group & Suntour, as a brand, went away .. decades ago.
the name has re appeared but just making suspension forks for OEM factory builds..




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onsay99

The older suntour accushift rear derailleurs were very sensitive to cable
anchoring position. Since you mentioned chainging the cable and housing
on the rear mech, the cable anchoring point is worth looking at as a
double check.

Bill Kapaun

Which do YOU call "low". The same as the rest of us?

IF it skips 2 when going to a smaller cog (physically), it indicates excessive friction in the cable/housing. You are relying on RDER spring tension to make the shift. Shifting the "other" direction is simply brute force, pulling the cable.
Unless this is a Low Normal RDER.

BCDrums

DS,

I did replace the entire cable run with Jagwire housing and a good Shimano cable. I find that I CAN get the chain to shift from 3 to 2 if I pull the exposed cable, or put my thumb on the derailler body. But both the old shifter and the new skip right over 2.

BCDrums

I understand that. I am calling Low the biggest cog (#6) and High the smallest cog (#1). Not low normal. Will re-examine the cable. I do find that I can go from 3 to 2 by moving the derailler body or exposed cable manually.

BCDrums

Wow, that's a blast from the past. Very informative, too. It addresses my problem, citing misadjustment of High limit. Will experiment. Thanks.

BCDrums

Yikes! If I had to sink $100 into components for this bike, I'd rather buy a used $100 bike!

In checking out some of the tips I have received, I noticed that the teeth on the upper pull are very worn, and were coated with gunk. I cleaned it off, and adjusted the B tension, and got it to work (that is, shift from 3 to 2, not skipping over 2) but it's inconsistent.

As I am reluctant to dump too much money into this bike, I will try @Iride01's suggestion of a thorough derailler cleaning, maybe I'll get lucky.



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Iride01 

You said your chain is "well worn". If so, then maybe it can't engage the cogs correctly. That can be your shifting issue. And if you've run a worn chain for long, then some of the rear sprockets and chain wheels might be worn too which will also affect how it shifts. So anything else you do might just be a very temporary fix.

BCDrums

This makes sense. I have worn out cogs before, and these don't seem worn to my eye, but the chain is, as measured.

Andrew R Stewart 

A SunTour equipped bike this old could very well have a replacement freewheel that is Shimano and not ST compatible. There's a reason why ST left the market, add 30 years of age and you have an old system that didn't work best even when perfectly speced. Andy

BCDrums

Andy, I found a page on Sheldon Brown's site that says the Suntour Accushift 6sp freewheel was identical dimension to a "regular" 6sp freewheel. I took "regular" to mean Shimano. But you're right about Suntour.

Sometimes I wish I was perfectly spaced.

canklecat

My only bike with Suntour Accushift components is an '89 Centurion Ironman with Suntour GPX 7-speed group. It was tricky getting satisfactory index shifting but switching from the original Suntour chain and freewheel to KMC Z72 chains and SunRace freewheels did the trick. The SunRace MFR30 (13-25) MFM30 (13-28) chromed freewheels are very good and work equally well with Suntour and Shimano groups.

However I haven't tried any 6-speed stuff so I don't know which SunRace freewheel might be comparable.

If you're still using the original Suntour chain, replace it with a decent KMC chain. The Z72 has been renamed, no idea what the current name is. But any compatible chain will be an improvement. I was surprised by how crudely made the original Suntour chain was. Most of the Suntour group was fine but the chain was junk.

fietsbob

2 problems are ... as you said, : 1, Old, & 2, Sun Tour..

BCDrums

I have ordered a compatible KMC chain from the LBS. Due to COVID protocol, I can’t just drive over and get it. Hoping to have it tomorrow.

canklecat

My LBS still allows in store shopping, with limits to two or three customers at a time. I visit about once a month just to buy something and show a little support. I usually buy a couple of tubes, maybe some snacks or electrolytes, chain lube, whatever consumable doodads they carry. Occasionally the LBS sells sample demo products, which are labeled "not for retail sale," but I buy 'em because it's usually half price or cheaper and presumably a high profit item for the shop. Seems fair. I got some great deals on mini pumps, gloves, handlebar wrap, etc., buying samples marked not for retail, after the promotional period was over or the product was discontinued. Hopefully the shop made some money. I got a good deal.

Most of my bike purchases this year have been online, usually stuff the LBS doesn't stock anyway. For example, the LBS carries some high end Continental tires but not the cheap Ultra Sport II and mid-priced GP Classic skinwalls I like.