Jackshaft Sick Bike Parts jackshaft issue

[wolframore]

I had a customer who had a loose jackshaft after about 300 miles, he’s had trouble with it since the start. We discovered the problem is there‘s too much play at the bearing because their shafts are under sized by 0.004-0.005”. I was on the phone with them and they stated they were aware of the problem and has had a lot of customers with same issue, what happens is the bearings spin on the shaft and wear making it worse and unusable. We thiught it was a bad bearing until disassembly showed what you see below. They suggested using loctite or dimpling the shaft. Pretty crappy. i ended up brazing bronze and turning to a tight slip fit. I have text message proof of them admitting they know of this problem and yet they still sell it... With all the sub par things like the undersized set screws. If the kit needs a special loctitie maybe they should ship with it. How about making it correct so we don’t have to fix a new kit.

 

[Chainlube]

Knurl the shaft to keep it from slipping on the bearing.

 

[wolframore]

Shouldnt have to fix a new kit to make it work. Our shaft measured 0.620 which was 0.005 under. Not even close to correct, in fact you can slide it on a new shaft and actually rock it side to side. Can’t believe these guys did absolutely nothing to make right and keep shipping this crap. It’s not a cheap kit. We needed some extras and it was about $200 for the kit which would be fine if there were no issues. All I’ve seen are issues. I will never again recommend this kit.

 

[5-7HEAVEN]

Hmmm.

It might be a mismatch between metric-sized and American-sized components.

The difference between a 5/8” shaft and a 16mm metric bearing is almost .005”.

The shaft would be.625”, whereas the 16mm bearing is .62992”.....

larger by .00492”.

However, you stated that the shaft had measured at .620”,
so my theory is shot.

 

[wolframore]

That’s a great theory, its a 99502HNR which is a standard bearing, 5/8” x 1 3/8” x 7/16”. Wish I could post a video of how much it rocks.

 

[5-7HEAVEN]

Either the vendor, their supplier or their manufacturer dropped the ball.

 

[wolframore]

Apparently they tried to mic a good shaft for me and couldn’t find one. Closest they could come was 0.621. For now the fix is to braze the shaft and turn it to a tight slide fit. There are a lot of kits out there that will fail and have issues keeping the chain that drives the crank. I’m no longer recommending these kits.

they suggested I use loctite or “dimple” which should hold until it wears out. I’m not willing to experiment. I build my reputation on solid builds that lasts.

heres some of the conversation

 

[Chainlube]

Machine the shaft a tenth of a mil over size and throw both parts in the freezer for a day. It'll never come apart after that.

 

[Frogslayer]

Machine the shaft a tenth of a mil over size and throw both parts in the freezer for a day. It'll never come apart after that.

What lol. You'd throw the shaft in the freezer and the bearings in an oven for a thermal fit.

 

[Chainlube]

What lol. You'd throw the shaft in the freezer and the bearings in an oven for a thermal fit.

No, both parts shrink and go together. They would kinda stay the same if you heat one and freeze the other. When they warm up, they expand and are tight together. "IF" it worked that way, you'd never want to heat your bearing.

Frozen crankshaft and speedy sleeve slip right together and once they warm up, never come apart.