Rigid fork swap advice please

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Russell160
Posts: 286
Joined: 4 Apr 2008, 6:36pm

Rigid fork swap advice please

Postby Russell160 » 9 Mar 2013, 10:45pm

I have a 26" Marin MTB that I'm converting for road/commuting and potentially laden touring use.

I have swapped out the suspension fork for a rigid alloy fork, suspension corrected, made by Van Nicholas see below. This was to reduce weight and bob when climbing. However, there are now two new problems;

i) I get brake judder
ii) I get pins and needles in my hands after a relatively short ride. (30 mins).
iii)There is a slight change in the frame geometry and my weight now seems more on the bars.

I am using continental 1.3 Sport Contact tyres. I have ergo handlebar grips and padded gloves.

I could live with the brake judder but not the pins and needles, especially as I am planning a C2C ride in June.

I am thinking the problems are being caused by the alloy fork which is very 'buzzy'. I am now thinking of swapping the alloy forks for a pair of rigid carbon forks (On ONe, see below)) that I already own. This will also involve converting from V brake to a mechanical disc brake on the front as the fork only has disk mountings; I plan to leave the rear as a V brake as there is no frame fitting for disks. . My thinking is a) carbon will be less buzzy and b) the frame geometry will be restored to its original set up taking a bit of weight off the bars.

My questions are:
1) Is my diagnosis correct: ie its the material the forks are made of thats causing the problem?
2)Will swapping to a carbon correct it?
3)Would steel be a better alternative and if so what fork could be people recommend? I shoud declare I'm biased towards the carbon because I've already got it.
4) If I go for a disk brake on the front would I be better going for a 160 or a 180 size disk? My concern is a 180 might be too severe??
5) Anthing else I should be thinkign about it??

Advice guidance welcome as always, thanks.

current fork: http://www.fatbirds.co.uk/19931/product ... black.aspx
Proposed new fork: http://www.on-one.co.uk/i/q/FOOOCAR/on_one_carbon_fork

Brucey
Posts: 42978
Joined: 4 Jan 2012, 6:25pm

Re: Rigid fork swap advice please

Postby Brucey » 9 Mar 2013, 11:09pm

Suspension corrected forks never work out quite corrected enough; well, too much or too little....

If your hands are going numb, in general I'd suggest to look at (definitely in this order);

1) Your position; there shouldn't be a lot of weight on your hands; if there is, you need to alter your position. A common mistake is to move the saddle forwards to get it closer to the handlebars; all this does is throw more weight onto your hands. The correct process is to set the saddle height, then set the saddle fore and aft, then to buy a new stem to get the bars in the right place wrt the saddle. When you are in the right position, you should just be resting your hands lightly on the bars when pedalling normally, not wrestling with them or propping yourself up with them.

2) Tyres; 1.3" tyres are rather narrow for this type of bike; less effort at 20mph than others? -yes, maybe, but not the best way to go quicker. I'd suggest ~1.75" ones with little tread and carefully chosen pressures as offering a good compomise between speed and comfort for road use on a stiff MTB frame. If you want to go faster, get your body more aerodynamic as a first priority.

3) Look at padded grips and gloves.

4) Look at different forks last. A noticeably resilient MTB-style fork is a rare commmodity in any material, and with a disc mount almost non-existent; in any event if you have a significant problem in 1-3 above, the fork won't make that much difference IME.

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

Jezrant
Posts: 734
Joined: 14 Dec 2007, 8:11pm

Re: Rigid fork swap advice please

Postby Jezrant » 10 Mar 2013, 9:03am

Assuming you've fitted the brake calipers properly on the new fork, the brake judder could be something's not right in the headset. I'd try re-adjusting the headset again. Also, check that the fork crown race is properly seated on the new fork.
I'd agree with Brucey that 1.75" will absorb a lot more road shock.
I know what you mean about how the rigid fork slightly changes the bike's geometry. I swapped a Rock Shox suspension fork for an Orange steel rigid fork on an Orange MTB, and it slightly lowered the front end. I wasn't too bothered, but I could use a different stem to compensate for the lower drop. I could imagine that if there's a significant difference between the two forks in terms of drop, that could well cause some discomfit. The Orange rigid fork also has a slightly different offset but I don't think that makes much difference as far as I can tell.

lowrider
Posts: 137
Joined: 21 Mar 2009, 2:25pm

Re: Rigid fork swap advice please

Postby lowrider » 10 Mar 2013, 10:39am

I would not have chosen an alloy fork or a carbon fork for a bike intended for fully loaded touring. By that I would take that you are thinking of front panniers, neither fork I would trust for that application. For commuting possibly these would do but the carbon fork looks particularly rigid and uncomfortable.

I went for a steel fork, there was little choice at the time only one had braze ons for racks that was the Thorn Mt Tura
http://www.sjscycles.com/thornpdf/Thorn ... kLoRes.pdf.

Not the best looking fork in the world but the only one that matched the specification and almost certainly more comfortable and stronger than a carbon or alloy fork.

I later saw some steel forks that were less expensive but these did not have braze ons, but for touring with only rear panniers or commuting these would have been fine.

niggle
Posts: 3425
Joined: 11 Mar 2009, 10:29pm
Location: Cornwall, near England

Re: Rigid fork swap advice please

Postby niggle » 10 Mar 2013, 6:14pm

The Kona P2 rigid chromo forks always had a good reputation, but can only find them here for about £99 with the postage: http://shop.konaworld.com/eu/products.p ... 26''-forks

MacBludgeon
Posts: 462
Joined: 6 Feb 2009, 4:19pm
Location: Farnborough, Hampshire, UK

Re: Rigid fork swap advice please

Postby MacBludgeon » 10 Mar 2013, 9:49pm

The two forks linked to have an AtoC difference of 20mm, this will equate to about a 1 degree variance in ST and HT angles. The longer fork will also lift the BB higher and vice versa. I don't know the specs of the previous suspension fork but would guess that it rode longer than 420mm a lot of the time. Say for example it rode at 440mm then your switch to the new fork will have rotated the whole bike around the BB from back to front so:-

your BB would have been lowered a bit
your bars would have dropped by 15-20mm
your saddle would be about 8-10mm further forward in relation to the BB/pedals
both ST and HT angles would have increased by 1 degree

As a result of the lower bars you will be bending further from the waist and so more weight would go onto your hands. To counteract that extra bend you would normally scoot your bum back a bit however you've actually scooted it forward which makes the weight change even more pronounced.

As others have mentioned the key part is keeping the saddle to BB/pedal relationship that works for you, then adjust other parts of the fit as required. It could be as above and a 20mm longer fork will restore your contact points and weight distribution. Certainly if you already have the forks then that would be a cheapish solution. But if you want to stick with the new forks then I'd guess that you'd need to move the saddle back by about 15mm and raise the bars by similar to give you a starting point.
nuns, no sense of humour

T44ISKN
Posts: 33
Joined: 13 Mar 2011, 8:51pm

Re: Rigid fork swap advice please

Postby T44ISKN » 12 Mar 2013, 4:33pm

I've got a spare set of steel MTB forks for v brakes. 1 1/8 th steerer. Black. Raked. Replaced them with some rigid carbon a few years back.

Not sure about the axle to crown measurement. Happy to measure if you're interested?

Russell160
Posts: 286
Joined: 4 Apr 2008, 6:36pm

Re: Rigid fork swap advice please

Postby Russell160 » 20 Mar 2013, 11:10am

Thank you all for your knowledgeable advice.

So the diagnosis is that its not just that the forks are alloy, it's mainly that they're too short and that's changed the geometry of the whole bike.

Thanks Brucey for the advice: I've moved the saddle back and fitted an adjustable stem, to raise the bars up and back a bit and this helps. The tingling has gone but I still feel a bit too far forward so a bit worried about long days in the saddle.

Thanks MacBludgeon for your tips and I got the tape measure out: A to C measurements are as follows:

Original Fork: 500mm, less sag 30mm?, average running lenght: 470mm.

Current Alloy Fork: 400

My Carbon Fork: 440

(Mt Tura Linked to : 430mm)

So, yes, I've taken 70 mm off the front end. So that's why my hands hurt.

The Van Nicholas forks were sold as Suspension Corrected but they're evidently a long way off. I've done some further digging on the Van Nicholas site and they appear to be a)Trekking forks and b)Fitted with Magura brakes with a brake booster which adds some rigiidity. ie so they're not a straight replacement for an MTB fork which is what they were sold as.
http://www.fatbirds.co.uk/5830/products ... -2013.aspx

(Please note I did not buy these from Fatbirds, it's just they'e got the pics on their site.)


I am still having brake judder and thanks Jezrant, have checked the headset etc and its ok. Have also tried fitting a V Brake Booster but with little effect.
I have come to the conclusion that its a combinatoin of a)me buying unwisely and b)being slightly missold. I have asked the retailers (On One) for a refund on the grounds of the brake judder and the flawed description and am waiting for reply.

My plan now, subject to your advice is:
*try the carbon fork for commuting purposes. This has an extra 40mm so should restore the geometry more or less.
*get a Mt Tura fork for if/when I go fully loaded touring.

Thanks for the offer T44, I have pMd you.

gloomyandy
Posts: 1096
Joined: 16 Mar 2012, 10:46pm

Re: Rigid fork swap advice please

Postby gloomyandy » 20 Mar 2013, 1:58pm

Hi,
I have a set of the onOne carbon forks on my touring bike (actually they are the 29er version). They give a very comfy ride when used with 40mm tyres (Marathon Supreme). I'm using them in an OnOne Inbred frame. Perhaps you could try the fork without messing around with the front brake (avoid steep hills!), to see if the ride and riding position improve?

Andy

Russell160
Posts: 286
Joined: 4 Apr 2008, 6:36pm

Re: Rigid fork swap advice please

Postby Russell160 » 20 Mar 2013, 8:07pm

Interestign Andy. Do you run them with V or disc brakes?
Mine onlly have disc fittings but thinking of getting v brake brackets (like Pace made) added. I am reluctant to have discs front and v back as it just seems odd and I imagine having such a difference in braking power could be difficult to control.
Once you start changing one thing on a bike it has so many unforeseen consequences doesn't it?

rogerzilla
Posts: 1603
Joined: 9 Jun 2008, 8:06pm

Re: Rigid fork swap advice please

Postby rogerzilla » 20 Mar 2013, 8:12pm

A Kona Project Two is a tried and tested steel fork for suspension replacements. Just get the right length.

gloomyandy
Posts: 1096
Joined: 16 Mar 2012, 10:46pm

Re: Rigid fork swap advice please

Postby gloomyandy » 21 Mar 2013, 10:58am

Hi, My InBred has discs front and rear. I have a sort of love/hate relationship with them! I love the way they work in the wet and that they provide really good control on steep hills (like the drop down to Greenhow hill to Pateley Bridge on the Way of the Roses), with a fully loaded bike. But I hate the way that the "auto adjust" feature (my brakes are Avid Elixir hydraulic), seems to mean that the pads often drag on the discs.