Author Topic: Slipping arm rests  (Read 1226 times)

quixoticgeek

  • Mostly Harmless
Slipping arm rests
« on: December 16, 2019, 12:07:27 am »

I have a pair of Profile Designs T2+ aero bars on my bike, unfortunately about every 250-300km I find the arm rests have rotated slightly downwards enough that my arm starts to fall off. So I have to stop, and move it back to its original position. This is starting to get really annoying.

I'm torquing the bolts to 6Nm.

Is there anything I can do to make these stay in the place I want them to be in? The bar is staying put, it's just the arm rest that moves. Curiously, the left one moves more than the right, tho the right does move too.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

bludger

  • Randonneur and bargain hunter
Re: Slipping arm rests
« Reply #1 on: December 16, 2019, 12:30:57 am »
6nm should be adequate as you say - that's what is used for shoe cleats so...

How about:

A: using loctite retaining compound in the relevant screws and bolts

B: using coarse sandpaper on surfaces such as between the arm rests and the bars: this could keep the rests from slipping

C: using some sorts of shim to create a tighter fit between bars and rests. I have made various gubbins work better by wrapping the relevant part of the bar with leftover rim tape (which does not compress in the same way e.g. electrical tape), including aero bars. Seems to work ok. Maybe old inner tube could be used somehow? I.e. slip the bars inside some lengths of old butyl tube and then clamp the rest mounts on.

I would definitely contact PD about this because this isn't right. If my cheapo Planet Flex ones can stay put for the duration, yours shouldn't have any problems. Seems like you're not the only one with issues https://forum.slowtwitch.com/forum/Slowtwitch_Forums_C1/Triathlon_Forum_F1/Aerobar_arm_rest_slipping_P3579849/

Someone in that thread recommends spraying hair spray on the inside of the clamp and leaving it for a day for added friction. Got any lying around? ;D the OP says it worked perfectly!
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Re: Slipping arm rests
« Reply #2 on: December 16, 2019, 09:20:57 am »
Carbon assembly paste is what I'd try, rather than loctite, it's what it is designed to do (stop things turning)

Re: Slipping arm rests
« Reply #3 on: December 16, 2019, 09:27:54 am »
I had a pair of Zipp Vukas that I never managed to get tight on one side.   I used to finish most TTs with one hand 1-2cm below the other.   To be fair the slip was usually caused when hitting bumps and there was less trouble on smoother surfaces.

I tried roughening surfaces, using carbon paste and loctiteing the bolts but never quite managed to resolve it.

Re: Slipping arm rests
« Reply #4 on: December 16, 2019, 10:07:42 am »

I have a pair of Profile Designs T2+ aero bars on my bike, unfortunately about every 250-300km I find the arm rests have rotated slightly downwards enough that my arm starts to fall off. So I have to stop, and move it back to its original position. This is starting to get really annoying.

I'm torquing the bolts to 6Nm.

Is there anything I can do to make these stay in the place I want them to be in? The bar is staying put, it's just the arm rest that moves. Curiously, the left one moves more than the right, tho the right does move too.

J

Not much you can do, it's a poor design.  I used to use them but got fed up with this happening and riding long distances with one elbow an inch lower than the other. 
Best option is to get rid of them and replace with Zipp Vuka which have a much beefier, 2-bolt clamp.  As Rob points out these are not perfect but they are the best ones available, far better than Profile T2.
The only way to stop the Profile pads slipping is to fix something on the handlebars below them to physically support them.  If you have the pads set so they are not above your bars, there's nothing you can do. 

zigzag

  • unfuckwithable
Re: Slipping arm rests
« Reply #5 on: December 16, 2019, 10:09:51 am »
i've got profile arm pads on one set of tribars and they tend to slip too. carbon grip paste helps a bit, but they still slip over bigger bumps. i consider it a bad design as the clamp is narrow and held by one bolt which is insufficient to keep it secure.

Re: Slipping arm rests
« Reply #6 on: December 16, 2019, 10:34:58 am »
Loctite on the clamped surfaces would probably be more effective than on the screws.

Though the first thing I’d try is getting a thin sheet of rubber inside the joint.




Re: Slipping arm rests
« Reply #7 on: December 16, 2019, 11:06:08 am »
Double-sided adhesive tape from 3M - the sort which has minimal substrate.
QG - if you PM me a postal address, I'll stick some in the post to you - I've got rolls of it coming out of my ears.

ETA - Any reason why you cannot drill a thru-hole through the clamp, tube and out of the other side and put a nut and bolt through the lot?
Or just drill the clamp and tube and pop a rivet in the hole.
Having firset checked and then checked again and again that the pads are exactly where your arms would like them to be.

Re: Slipping arm rests
« Reply #8 on: December 16, 2019, 01:40:21 pm »
Basically they are ok for doing TTs on reasonably smooth roads, which is what they are designed for.  When you try to use them on lanes or other bumpy roads, they are not up to it.

quixoticgeek

  • Mostly Harmless
Re: Slipping arm rests
« Reply #9 on: December 16, 2019, 01:51:55 pm »

Looked at the zipp vuka But they require the arm rest to be over the base bar, which for me it isn't. Because I'm quite small, I have the bars quite far back, in fact I'm PBP legal without needing to change their position. It's not the most aero way they could be setup, but it's comfortable for long periods this way.

Gonna try the tape idea. If that doesn't work, I might try a cross brace from one support to the other.

J

--
Beer, bikes, and backpacking
http://b.42q.eu/

bludger

  • Randonneur and bargain hunter
Re: Slipping arm rests
« Reply #10 on: December 16, 2019, 02:04:23 pm »
I would definitely give the hairspray approach a go too - if it worked for the person in that other thread it might be just the thing.

You could always walk into Dutch boots and spray some on the clamps while no one is looking if you have none....
YACF touring/audax bargain basement:
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Ban cars.

Re: Slipping arm rests
« Reply #11 on: December 16, 2019, 04:04:57 pm »

Looked at the zipp vuka But they require the arm rest to be over the base bar, which for me it isn't.


That's not correct - they are fully adjustable.  My pads are behind my base bar.
Here's a pic from Burgas

Re: Slipping arm rests
« Reply #12 on: December 16, 2019, 07:18:40 pm »
I had a pair of Zipp Vukas that I never managed to get tight on one side.   I used to finish most TTs with one hand 1-2cm below the other.   To be fair the slip was usually caused when hitting bumps and there was less trouble on smoother surfaces.

I tried roughening surfaces, using carbon paste and loctiteing the bolts but never quite managed to resolve it.

Hi Rob.
I have a new build gong into production imminently and they have specced Zipp vukas for the aero bars. The bike is for touring and ultras. Should I get it switched out?
Sorry to muscle in on your thread QG.

Just to add that on my current set up I have Deda parabollica and they have been rock solid, no slipping (married to a Fred bar)
That is aside from when my top cap gave out this Summer while I was leaning on the bars, almost very ugly.
I think my bike builder had an issue with incorporating the Dedas on the new build, I'll chase it up with him. I really don't like the sound of loose aero bars.
often lost.

Re: Slipping arm rests
« Reply #13 on: December 16, 2019, 11:27:29 pm »
I'm not Rob but, having tried a few, zipp vuka alumina are what I would recommend.
I think Rob has been unlucky. Most people don't have problems with them.

Re: Slipping arm rests
« Reply #14 on: December 17, 2019, 09:12:09 am »
I had a pair of Zipp Vukas that I never managed to get tight on one side.   I used to finish most TTs with one hand 1-2cm below the other.   To be fair the slip was usually caused when hitting bumps and there was less trouble on smoother surfaces.

I tried roughening surfaces, using carbon paste and loctiteing the bolts but never quite managed to resolve it.

Hi Rob.
I have a new build gong into production imminently and they have specced Zipp vukas for the aero bars. The bike is for touring and ultras. Should I get it switched out?
Sorry to muscle in on your thread QG.

Just to add that on my current set up I have Deda parabollica and they have been rock solid, no slipping (married to a Fred bar)
That is aside from when my top cap gave out this Summer while I was leaning on the bars, almost very ugly.
I think my bike builder had an issue with incorporating the Dedas on the new build, I'll chase it up with him. I really don't like the sound of loose aero bars.

I had parabolicas on my first race bike and was quite happy.   The custom TT bike had Vuka base bars and extensions.   I was low down and very far forward so there was quite a lot of weight levered out at the wrists.   Don't get me wrong, they didn't always slip but had a tendency to move when I hit a bump at speed, usually on a stretch of road in Surrey/Hants the Frank knows very well.

The pros are that they are very adjustable and the pads are very comfortable.   I did get through a few sets of pads but the bike was on the turbo all Winter so they got soaked quite regularly - they do go through the washing machine.     

Re: Slipping arm rests
« Reply #15 on: December 17, 2019, 02:09:42 pm »
Thanks guys.
Is it because you are clamping onto carbon so not yuking down on the bolts?
My Fred bar is steel and the new bars are aluminium so I can give it a good old wrench.

Never had to change pads. Still 2 TCR worth of snot and dribble on the current set.
often lost.

Re: Slipping arm rests
« Reply #16 on: December 17, 2019, 04:54:09 pm »

Is it because you are clamping onto carbon so not yuking down on the bolts?


My set up was ally on ally.   Zipp seem to prefer Torx bolts to hex keys as they want to avoid ham fisted people like me stripping threads.   What this means, in reality, is that I can't get them tight enough.

quixoticgeek

  • Mostly Harmless
Re: Slipping arm rests
« Reply #17 on: December 17, 2019, 09:10:46 pm »
Thanks guys.
Is it because you are clamping onto carbon so not yuking down on the bolts?
My Fred bar is steel and the new bars are aluminium so I can give it a good old wrench.

The only carbon on my bike is the derailleur. The bars are ali.

The bolts have some threadlok on there.

Quote
Never had to change pads. Still 2 TCR worth of snot and dribble on the current set.

I changed the set of pads that were on there when i got the bars, as they were falling apart, The new pads have a different design, which works better. There are a bit squashed on one side, but are still usable. I may treat myself to new ones in the new year.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Karla

  • car(e) free
    • Lost Byway - around the world by bike
Re: Slipping arm rests
« Reply #18 on: December 17, 2019, 09:51:12 pm »
I must have used a couple of pairs of Zipp Vukas for about 30,000 miles now, half of them with a dry bag strapped under them, and I haven't had a problem with them slipping. 

For fore/aft pad adjustability, I think the new ones might be less good than the older version that Frank, Rob and I have all used.  Then again they might be just the same.  If not though, you could look for a pair of the previous model.

quixoticgeek

  • Mostly Harmless
Re: Slipping arm rests
« Reply #19 on: December 17, 2019, 10:00:31 pm »

Has the vukas design been changed? All the photos I can find seems to show the clamp that attaches to the base bar also supports the arm rests.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Karla

  • car(e) free
    • Lost Byway - around the world by bike
Re: Slipping arm rests
« Reply #20 on: December 17, 2019, 11:39:10 pm »
Yes the design has been changed.  The old ones looked like this.  I'm pretty sure you could move the inner part of the pad clamp fore and aft on the top mount version.  Frank will have to confirm though, as I had the bottom mounts.



Re: Slipping arm rests
« Reply #21 on: December 18, 2019, 10:27:51 am »
Yes, they are fully adjustable.
in the picture of my set up, above, the pads are mounted on the extensions a couple of inches behind the base bar. When riding I can reach the tops in front of the pads.

Rob's TT setup is way more aggressive than anything you would see on an ultra bike with far more weight on the pads (because his saddle would be much further forward). The bumps he mentioned in the a31 have made my profile T2 pads slip regularly! I still think he was unlucky that he had one pad slip as they are rock solid. The key thing is two bolts, not one, and a big contact area that you can load up with assembly paste.

I'm not on commission from Zipp so, by all means, get something else first. Then get the Zipp ones later when you've found the others aren't as good (that's what I did)!

Re: Slipping arm rests
« Reply #22 on: December 18, 2019, 11:00:55 am »