[Closed] Short stem with steerer bolts bigger than M4?

I've never seen a stem that uses M4 bolts. Are you confusing the size of allen key required with the bolt size?

Presumably you’re talking about 4mm head bolts?

I have the same bike as you (although this problem relates to the stem / steerer rather than the bike) and haven’t had any issues with stems coming lose. In fact both stems I’ve run on there have had a torque limitation etched into them - off the top of my head I can’t remember if 5nm or 10nm.

Raceface aeffect was my 40mm one that came with the bike (for a 35mm diameter h/bar) and I recently swapped it out for a 32mm long Raceface Turbone as I was looking to shorten the reach to the bars and that was as short as I could get with a 35mm diameter bar.

Both just did what a stem should do - tighten to the listed torque and away you go.

Presumably your steerer isn’t covered in grease where the stem is trying to grip it, and you’ve done the middle bolt up until the point there is no longer any play?

If its a DH bike can you run a direct mount stem?

If its a DH bike can you run a direct mount stem?

Bird Aeris isn’t a dh bike and will have single crown forks in the main.

try some carbon grip paste on the steerer / stem

I had this reoccurring issue on a BMX...

Assuming you have the spacers all set correctly, try removing all the bolts, give the stem threads & bolts a thorough clean and then relube the stem bolts & torque it up as per manufacturers recommended settings.

🤞

Bird Aeris isn’t a dh bike and will have single crown forks in the main.

Ignore me, I am a muppet, I read DH Bike, not DH run.

Its not a common issue, I would strip clean and inspect, if no obvious issues I would suggest trying another stem.

Trek issues a service bulletin warning friction paste can work its way down into the headset and cut into the fork.

Is the steerer just a fraction too long. I have had the same problem and put a spacer on top of the stem just to try. The top cap was just touching the top of the steerer when torqued down so the play was always in there. The spacer solved the problem so left it on rather than take a bit off the steerer.

Is the steerer just a fraction too long. I have had the same problem and put a spacer on top of the stem just to try. The top cap was just touching the top of the steerer when torqued down so the play was always in there. The spacer solved the problem so left it on rather than take a bit off the steerer.

I've had exactly that as well. Only a tiny bit long so it felt perfect in the workshop and riding round the block. Out on the trails and the play was very evident.

Assuming you have the spacers all set correctly, try removing all the bolts, give the stem threads & bolts a thorough clean and then relube the stem bolts & torque it up as per manufacturers recommended settings.

This, plus make sure the surfaces of the steerer and stem are totally clean (use IPA). They'll probably have a bit of grease on after you've installed a headset race no matter how careful you are. You could use some carbon grip paste once you've made sure both surfaces are clean. Oh and this:

Is the steerer just a fraction too long.

Plus make sure the crown race is on correctly (if it's happened multiple times this probably isn't the problem). You could try another stem but really it's not the size of the fastener. They're fully up to the job.

Chances are its using shitty chinesium bolts and they dont give a you a decent axial load, despite them being torqued correctly. Try replacing them with a better quality bolt. If they have built in washers, they are likely a reduced head size, so you will have to go the stainless route, if not, normal cap heads.

Thanks all, and yes Simondbarnes you are correct, I meant to say m5 (what the stem uses). Easy to get the M number and allen key size muddled!

I have tried all of the above unfortunately! Removed the stock bolts and has SS ones in for a while. I currently have rainbow ti ones in for the extra bling... definitely tightened up beyond the suggested torque though. New headset bearings too.

Had the same issue when I ran this stem on my hardtail with rigid forks on, but the issue was even more prevalent and I would have to retighten just riding XC.

I will try giving it another clean and tighten up (definitely no spacer/top of steerer tube interference issues), but given that it's done it on other bikes it seems to just be that the stem isn't up to scratch to taking a lot of abuse. (I've got an old and very heavy Funn Rippa on the hardtail now, no issues with slippage but the bolts are monster size and the stem weighs a ton!)

What’s the recommended torque on the steerer clamp bolts?

I've got the same stem and never had an issue. I've just spent 8 days hammering it in the Alps and it's still fine. There must be something else up.

I'm sure Mine's torqued to the recommended torque (which isn't that high).

Sounds like time to try another stem for sure - could you just borrow one?

Actually just thought some of my spacers are slightly too fat (diameter) to sit flush against the top of the stem.

Check they're all sitting down flush and square before you pre load the top cap, it's where it angles up from the flat top that they get held up on.

The bolts are done up to the point where they feel like they’ll strip something if I go anymore.

definitely tightened up beyond the suggested torque though

I'd suggest this may be a mitigating factor. If you are having slippage problems then horsing it up isn't fixing anything.

It could be the steerer clamp is over the max tolerance or mishapen. Either way, try another stem, if this one has been doing it for years stop flogging a dead horse.

What’s the recommended torque on the steerer clamp bolts?

Usually about 5Nm