front wheel flexes whilst climbing? cause

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Brucey
Posts: 35201
Joined: 4 Jan 2012, 6:25pm

Re: front wheel flexes whilst climbing? cause

Postby Brucey » 9 Sep 2019, 8:31pm

the USE hub is almost certainly a rebranded SP hub; SP make hubs that are sold under a variety of names.

If you think the commuting wheel is different from the other one then you could try swapping the wheels between the bikes and see how you get on. I would be very surprised if it is not in fact some difference in the forks as previously discussed.

That said, the flanges on the SP hubs are often very close to one another and this makes the wheel less stiff than it should be. SON now make a wider bodied hub than they did before, specifically to increase the wheel stiffness.


With narrow spaced flanges the wheel is less strong laterally. Interestingly if the flanges are narrow enough, you can get most rims (even quite stiff modern ones) to self-pringle i.e. they can suffer an elastically initiated failure via Euler buckling. However before this failure actually occurs, there is a range of (very high) spoke tensions in which the wheel is simply less stable than it usually is; in this state it will be 'difficult' to true it up and it may also deflect more than normal under a lateral load. It is maybe worth double checking the spoke tension in that wheel; it is easy enough to 'overdo it' with a rim like an Archetype.

BTW if your SP hub has gone bad, ISON offer a 'refurb' (on a loose hub posted to them) for about £25. Worth looking into if you think the bearings have gone bad.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

fatboy
Posts: 3342
Joined: 5 Jan 2007, 1:32pm
Location: North Hertfordshire

Re: front wheel flexes whilst climbing? cause

Postby fatboy » 10 Sep 2019, 1:39pm

I've got SP hubs on two bikes (32 spokes, Chrinra and LX17) and haven't noticed flex when riding and I'm 80kg plus. I have done the exchange that Brucey talks of as one got play in the bearings.
"Marriage is a wonderful invention; but then again so is the bicycle puncture repair kit." - Billy Connolly

Brucey
Posts: 35201
Joined: 4 Jan 2012, 6:25pm

Re: front wheel flexes whilst climbing? cause

Postby Brucey » 10 Sep 2019, 11:58pm

BTW the OP has a problem because the brakes rub. Apologies if this is b.obvious (and maybe it has been addressed upthread) but how the brakes are set up will affect the chances of brake rub too.

There are some brakes (e.g. with mismatched levers and calipers, or levers that can't pull enough cable for some reason ) which cannot be set up with a generous running clearance to the rim. These brakes are of course much more likely to rub.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

martinn
Posts: 307
Joined: 1 Dec 2012, 8:20pm

Re: front wheel flexes whilst climbing? cause

Postby martinn » 11 Sep 2019, 9:50am

Yes my issue is that I have had to back the brake off a lot, which happened previously and is now at 4-5mm.
The brakes I have are Campag Athena 11speed with a BR650 front brake, as I didn't like the way that the tekros that I had on previously used to bend.

I will be changing over the wheels today and see how that goes, to see if I still get the same amount of flex.

Dismantling the Wheel and sending the hub off for refurbishment is an option, but, it means that that I would need to be swapping wheels over whilst its out of action, I would need to rebuild the wheel, (No I not patient enough to do it myself!), and if its just what happens within the design parameters, I would be repeating it year on year, which is annoying to say the least.

So would the Son Delux with the wide flange likely with a suitable rim (Open to suggestions), have less potential flex?

regards

Martin

Brucey
Posts: 35201
Joined: 4 Jan 2012, 6:25pm

Re: front wheel flexes whilst climbing? cause

Postby Brucey » 11 Sep 2019, 10:08am

the wheel with the SON will be about twice as stiff (laterally) as one with closer spaced flanges. However we don't know for sure if the wheel build itself is the major source of flex you are seeing or if it is something else.

Swapping wheels (with similar rims and spoking etc) about between bikes will give you confidence to proceed in a given direction (or not). If you can do, try a conventional wheel too; this ought to be similar in stiffness to one built with a widebody SON.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

martinn
Posts: 307
Joined: 1 Dec 2012, 8:20pm

Re: front wheel flexes whilst climbing? cause

Postby martinn » 14 Sep 2019, 9:35am

Update,

I moved the SP hub onto my Fixed with the Steel fork, almost no movement.
I moved the USE hub to my Rourke with the carbon fork, massive amount of movement.- This has no movement on the steel fork.
I put the hand build font wheel (Non dynamo) onto the carbon fork,(28 hole) not as bad movement comparatively, but when climbing hard out of the saddle, I got brake rub.

Now I say comparatively, as there was at least 4-5mm of clearance either side of the wheel for all three tests.
Additional, when I freely span the two dynamo hubs, in the same fork (I tried both) with approximately the same amount of force, the SP hub span for a significantly shorter period, and ended with a sort of "shudder", the USE ended with a significantly less pronounced "shudder"(Sorry probably not the right term but fits in my mind at least).- any significance

Interestingly, I got more brake rub when I pushed down with my right hand leaning the bike to the right. Is this significant, or is it because I am right handed and can push harder with my right had. This was the same for all three tests.

when I first got this bike, 5 years ago, I had mavic wheel with only 18 spokes at the front, and I did have a small amount of brake rub then if I really pushed it hard, but the blocks were not as backed off.

Thinking about this more, I did have a low speed "off" on this bike, but I cant remember how soon after this the wheel started rubbing. I don't recall it being straight away.

So new fork required?
Its carbon is it going to fail?
can I remove the existing headset and reuse?
IF I need a new fork- suggestions?, I believe its 1 1/8 and needs to take mudguards, its for my "best " bike, which tends to be used for audax riding

thanks

Martin

Brucey
Posts: 35201
Joined: 4 Jan 2012, 6:25pm

Re: front wheel flexes whilst climbing? cause

Postby Brucey » 14 Sep 2019, 9:42am

sounds like you probably could do with a new fork. If the fork (under static test) deflects more now than it used to, and more particularly to one side more than the other, then this is strongly suggestive of a crack or other problem.

Needless to say if the fork lets go in use it is probably going to cause a visit to hospital (if you are lucky) or a longer visit to a wooden box (if you are not lucky).

1-1/8" headset parts should swap to a similar fork. What size tyres are you using and what do you find acceptable mudguard clearance? {Or more simply, what brake drop settings are you using?]

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

martinn
Posts: 307
Joined: 1 Dec 2012, 8:20pm

Re: front wheel flexes whilst climbing? cause

Postby martinn » 14 Sep 2019, 11:02am

Currently Shimano BR650 deep drop brake.
Clearance, with guards is "interesting". I can run 28mm GP4 seasons no problem, however 28mm GP4000II, on the other hand need a little modification of the mudguard to fit.
Rear is also 28mm, but I could probably squeeze a 30mm in there, depending on the "reality" of the size.

I did have a thought of having a radical rethink of the front end, and use a through axle? But I think that most of the fork that might fit would be disc specific.

Yes the scenario with a breaking fork does have me being nervous....

Thanks

Martin