Thru axle too tight...help

**farmguy** · 09-25-2018, 01:55 PM

Transition throttle with SRAM XO, I have a set of American Classic wheels that I had re-dished for boost added a problem solvers boost kit to fit the frame so rebuilt the hub with bearings spacers etc. When I tighten the axle down I get pressure or tension when ever I spin the pedals in reverse, the wheel will spin free in forward or coast but spinning the pedals backwards will cause rear wheel to spin in reverse as well. Ideas? is the preload on my bearings too much? Ive ruled that out as I can spin by hand and the wheel spins forward for quite a while. As soon as I back of the torque on my thru axle maybe 1/8 of a turn, it spins free.

Axle is a Syntace X-12

**toast2266** · 09-25-2018, 02:16 PM

Boost spacer dragging on freehub body?

**El Chupacabra** · 09-25-2018, 02:19 PM

With the axle tightened down, if you turn the pedals and let the rear wheel spin, does the chain keep moving (and continue to rotate the cranks)? In other words -- does the freehub properly freewheel?

**detrusor** · 09-25-2018, 02:21 PM

Lube the free hub seal.

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**farmguy** · 09-25-2018, 02:55 PM

Boost spacer is only on brake side so no issue there.
I can spin the pedals and stop, wheels spins and chain/crank do not move.
Everything is lubed, and lubed again.

**mntlion** · 09-25-2018, 03:22 PM

am classic hub might be getting tighter as you tighten axle? how is it if you back off the hub bearings (so it feels loose when not in the frame) and use the axle to tighten it down?

I had a old wheel set that needed this. Maybe AM classic, maybe mavic?

**dannynoonan** · 09-25-2018, 10:34 PM

I've had this happen, often is either a freehub dust seal that went back in crooked or pinched, or a missing bearing spacer on/in the freehub. Some A.C. hubs have a very small, think 1mm spacer, that looks like a washer that sits against the freehub bearing. If it gets lost, the whole thing binds up when you tighten the axle. Exact symptoms that you describe.

You said it's the non drive side only, but did you put it on yourself? If a shop did it for you they may have lost something in the process of figuring out how to put it all together.

**jono** · 09-25-2018, 10:54 PM

What you describe is too much freehub drag, not too much bearing drag, so the bearings are probably fine. Spinning backwards when you pedal backwards literally means the drag in the bearings is less than the drag in the freehub. Does more tightening of the axle get the hub to stop freewheeling (will the wheel spin the pedals if you tighten it more)?

I had one doing that, turned out it was missing a spacer so the axle tension was pulling things together until the freehub was pinched into compression which kept it from spinning free. (The spacer is there to transfer the load to the bearings instead.) The telltale was that with enough axle torque it got really bad and with it barely snug it would function normally. If it does that the hub probably went back together without all its parts.

**mntlion** · 09-26-2018, 08:00 AM

Also: Is AM classic done as a company? If needed I have some hub parts still floating around in my parts box

**farmguy** · 09-26-2018, 09:36 AM

Originally Posted by jono

What you describe is too much freehub drag, not too much bearing drag, so the bearings are probably fine. Spinning backwards when you pedal backwards literally means the drag in the bearings is less than the drag in the freehub. Does more tightening of the axle get the hub to stop freewheeling (will the wheel spin the pedals if you tighten it more)?

I had one doing that, turned out it was missing a spacer so the axle tension was pulling things together until the freehub was pinched into compression which kept it from spinning free. (The spacer is there to transfer the load to the bearings instead.) The telltale was that with enough axle torque it got really bad and with it barely snug it would function normally. If it does that the hub probably went back together without all its parts.

This seems to be the case, free wheeling works fine. It just seems to be cassette causing the drag it that's possible. I have a spacer in the hub but as many times as Ive had it apart....who knows. Right now I have the spacer inside the hub shimming the hub a bit. Next question, is there only one spacer made, 1 mil? And yes AM is done as a company so parts are shit to find.

**jono** · 09-26-2018, 10:11 AM

If you can get it to change with axle tension then look for a spacer issue, if not then it's probably a seal etc. like Toast and others said. A dragging seal isn't really going to get worse with more axle tension, I wouldn't think.

**donutlynx** · 09-26-2018, 10:48 AM

Sounds like it could be an axle end cap on the drive side that was installed in the incorrect order or slightly crooked. Similar to what dannynoonan describes.

**farmguy** · 09-26-2018, 11:13 AM

Ill give everything a check, leaving for a trip so it will have to wait a few days.

Thanks guys

**farmguy** · 10-03-2018, 10:51 AM

I finally got around to checking end caps and spacers. End caps all look ok but from reading the rebuild instructions on Ac's site they show 2 spacers installed in read hub, mine only has one so now I need to search for a 5mm spacer. Let the fun begin. Thanks again.