Fork Clearance

Brendo09
Posts: 16
Joined: Tue Mar 13, 2018 7:28 pm

Fork Clearance

Postby Brendo09 » Mon Jun 25, 2018 3:13 pm

This is a quick one... I've got an Oppy A4, and the front fork is tight with a Hutchinson Fusion5 28mm tyre (which measures closer to 25mm).

Am I bound to 23mm tyres, or is there a bodge I can do?

If I have to get a new fork I might as well get a new bike.

User avatar
10speedsemiracer
Posts: 1204
Joined: Sat Feb 11, 2017 7:38 pm
Location: Melbourne, in the suburbs, near some hills

Re: Fork Clearance

Postby 10speedsemiracer » Mon Jun 25, 2018 3:22 pm

Try one of the skinnier 25mm tyres. I like a Vittoria and they sit fairly close to spec, but that also depends on the wheels.

Over the weekend, I fitted a pair of 25mm Vittoria Zaffiros to some Concept SL rims, sat at 25.37mm at 100psi. Also fitted a pair of Schwalbe One 25mm to some old school Alesa rims, which ended up reading 24.88mm at 100psi.

So you can probably avoid the bone-jarring 23mm, but not by a lot.

And just out of curiosity I measured some 28mm Vittoria Zaffiro rubber I have on my training bike which has aero rims, and these measured 28.64mm at 100psi.
Mmm, SunTour

RobertL
Posts: 694
Joined: Wed Feb 17, 2016 3:08 pm
Location: Brisbane

Re: Fork Clearance

Postby RobertL » Tue Jun 26, 2018 9:04 am

I have a 2011 Oppy A5. I run 25mm Contis and they fit with plenty of room. I've used both Gatorskins and GP4000S2s.
Image

uart
Posts: 1536
Joined: Sat Jan 02, 2016 9:15 pm
Location: Newcastle

Re: Fork Clearance

Postby uart » Tue Jun 26, 2018 11:17 am

Brendo09 wrote:This is a quick one... I've got an Oppy A4, and the front fork is tight with a Hutchinson Fusion5 28mm tyre (which measures closer to 25mm).

Am I bound to 23mm tyres, or is there a bodge I can do?

If I have to get a new fork I might as well get a new bike.


It depends on exactly how tight is "tight", and close to 25 is "closer to 25".

If I read it correctly you are currently running something larger than 25 and still have some clearance, albeit not as much as you would like. In that case it shouldn't be necessary to go all the way down to 23c, most brand's 25c should be ok.

uart
Posts: 1536
Joined: Sat Jan 02, 2016 9:15 pm
Location: Newcastle

Re: Fork Clearance

Postby uart » Tue Jun 26, 2018 11:22 am

Brendo09 wrote:Am I bound to 23mm tyres, or is there a bodge I can do?

In regard to this question. Is the clearance issue most critical laterally (to the fork blades) or radially (to the bottom of the brake calipers)?

Brendo09
Posts: 16
Joined: Tue Mar 13, 2018 7:28 pm

Re: Fork Clearance

Postby Brendo09 » Wed Jun 27, 2018 5:58 pm

Sorry about the delay.

I've just tried successfully to fit the 28mm to the rear, so that's good. My calipers measured the width at just under 27mm.

I'll buy a 25mm and try to fit that to the front. Previously the rub was on the top of the fork, the brake calipers cleared it sufficiently.

I won't run the risk of being widely harassed or ridiculed with a 25 / 28mm front rear tyre combo will I? I figure that the sight of me in my cheap lime green Chinese kit will distract attention from the bike itself :)

uart
Posts: 1536
Joined: Sat Jan 02, 2016 9:15 pm
Location: Newcastle

Re: Fork Clearance

Postby uart » Wed Jun 27, 2018 8:15 pm

Brendo09 wrote:I'll buy a 25mm and try to fit that to the front. Previously the rub was on the top of the fork, the brake calipers cleared it sufficiently.

Ok, so it was rubbing at the top of the forks rather than the sides of the fork blades. That's actually better because it means that getting a small buckle wont screw you. Yeah give it a try with 25c, it will probably work ok.

I won't run the risk of being widely harassed or ridiculed with a 25 / 28mm front rear tyre combo will I?

No it's not all that uncommon to run slightly narrower on the front. With the typical weight distribution about 60/40 (R/F) it actually makes some sense.

Brendo09
Posts: 16
Joined: Tue Mar 13, 2018 7:28 pm

Re: Fork Clearance

Postby Brendo09 » Thu Jun 28, 2018 12:02 pm

Happy days. Picked up a 25mm Pirelli from the local shop, and it fits in there like a glove, with about 1mm to spare to the top of the forks.

Now to give it a whirl and see if it can't stop me from buying something with bigger tyres anyway :)

User avatar
hamishm
Posts: 586
Joined: Wed Oct 28, 2009 11:31 pm

Re: Fork Clearance

Postby hamishm » Thu Jun 28, 2018 12:31 pm

Brendo09 wrote:Happy days. Picked up a 25mm Pirelli from the local shop, and it fits in there like a glove, with about 1mm to spare to the top of the forks.

Is this still going to be comfortable when the front tyre picks up dirt or other debris?

Brendo09
Posts: 16
Joined: Tue Mar 13, 2018 7:28 pm

Re: Fork Clearance

Postby Brendo09 » Thu Jun 28, 2018 12:42 pm

hamishm wrote:
Brendo09 wrote:Happy days. Picked up a 25mm Pirelli from the local shop, and it fits in there like a glove, with about 1mm to spare to the top of the forks.

Is this still going to be comfortable when the front tyre picks up dirt or other debris?


I'm going to say yes.

I'm also going to find out. Hopefully it's still a resounding yes.

uart
Posts: 1536
Joined: Sat Jan 02, 2016 9:15 pm
Location: Newcastle

Re: Fork Clearance

Postby uart » Thu Jun 28, 2018 1:14 pm

hamishm wrote:
Brendo09 wrote:Happy days. Picked up a 25mm Pirelli from the local shop, and it fits in there like a glove, with about 1mm to spare to the top of the forks.

Is this still going to be comfortable when the front tyre picks up dirt or other debris?


I was just about to say the same thing, 1mm is pretty tight, that's for sure.

You'll be fine on dry pavement, but if you have to go through any patches of mud/crap then it might get annoying. You wont need much crap to stick to the tyre before the old "rub-rub-rub" starts.

User avatar
RonK
Posts: 10314
Joined: Mon Aug 24, 2009 2:08 pm
Location: If you need to know, ask me
Contact:

Re: Fork Clearance

Postby RonK » Thu Jun 28, 2018 1:16 pm

Brendo09 wrote:
hamishm wrote:
Brendo09 wrote:Happy days. Picked up a 25mm Pirelli from the local shop, and it fits in there like a glove, with about 1mm to spare to the top of the forks.

Is this still going to be comfortable when the front tyre picks up dirt or other debris?


I'm going to say yes.

I'm also going to find out. Hopefully it's still a resounding yes.

1mm? Sorry, but experience tells me otherwise.
Cycle touring blog and tour journals: whispering wheels...

User avatar
10speedsemiracer
Posts: 1204
Joined: Sat Feb 11, 2017 7:38 pm
Location: Melbourne, in the suburbs, near some hills

Re: Fork Clearance

Postby 10speedsemiracer » Thu Jun 28, 2018 1:31 pm

1mm is insufficient clearance, should be aiming for 3mm as a minimum. I think you may be destined for a 23mm on the front after all...
Mmm, SunTour

User avatar
P!N20
Posts: 905
Joined: Thu Jul 22, 2010 6:50 pm

Re: Fork Clearance

Postby P!N20 » Thu Jun 28, 2018 1:59 pm

10speedsemiracer wrote:1mm is insufficient clearance, should be aiming for 3mm as a minimum.


Say what now?

Image

User avatar
10speedsemiracer
Posts: 1204
Joined: Sat Feb 11, 2017 7:38 pm
Location: Melbourne, in the suburbs, near some hills

Re: Fork Clearance

Postby 10speedsemiracer » Thu Jun 28, 2018 2:02 pm

P!N20 wrote:
10speedsemiracer wrote:1mm is insufficient clearance, should be aiming for 3mm as a minimum.


Say what now?

Image


Whilst aesthetically pleasing, my head hurts just looking at it...hoping you don't ride near wet tan bark PIN20...
Mmm, SunTour

User avatar
P!N20
Posts: 905
Joined: Thu Jul 22, 2010 6:50 pm

Re: Fork Clearance

Postby P!N20 » Thu Jun 28, 2018 2:21 pm

^ Not mine. There's no way I'd ride with unwrapped bars ;)

Brendo09
Posts: 16
Joined: Tue Mar 13, 2018 7:28 pm

Re: Fork Clearance

Postby Brendo09 » Thu Jun 28, 2018 2:58 pm

3mm clearance minimum? Argh.

Looks like fair weather riding then. And another tyre to buy.

uart
Posts: 1536
Joined: Sat Jan 02, 2016 9:15 pm
Location: Newcastle

Re: Fork Clearance

Postby uart » Thu Jun 28, 2018 3:01 pm

P!N20 wrote:^ Not mine. There's no way I'd ride with unwrapped bars ;)

Ouch! Even just a small increase in tyre pressure will make them rub when they're that close.

User avatar
Thoglette
Posts: 4211
Joined: Thu Feb 19, 2009 1:01 pm

Re: Fork Clearance

Postby Thoglette » Thu Jun 28, 2018 5:23 pm

Brendo09 wrote:3mm clearance minimum? Argh.

Looks like fair weather riding then. And another tyre to buy.


Now I'll push for 3mm on the sides as your wheels and tyres flex as you pedal hard. But with the top clearance it's not so much the size as the quality. Is it one spot under the brake caliper? Or is it cigarette paper thin all around? (Like the photo above).

The real question is: If the tyre picks up a piece of "stuff" how likely is to jam?
Stop handing them the stick! - Dave Moulton
"People are worthy of respect, ideas are not." Peter Ellerton, UQ

Brendo09
Posts: 16
Joined: Tue Mar 13, 2018 7:28 pm

Re: Fork Clearance

Postby Brendo09 » Thu Jun 28, 2018 5:59 pm

Thoglette wrote:
Brendo09 wrote:3mm clearance minimum? Argh.

Looks like fair weather riding then. And another tyre to buy.


Now I'll push for 3mm on the sides as your wheels and tyres flex as you pedal hard. But with the top clearance it's not so much the size as the quality. Is it one spot under the brake caliper? Or is it cigarette paper thin all around? (Like the photo above).

The real question is: If the tyre picks up a piece of "stuff" how likely is to jam?


Just poked a hex key in the gap to see, and it looks like my mm is actually between 2 and 3 mm. The tightest part is right at the top of the forks, directly under the head tube. There's clearance galore on the sides and on the brake calipers.

This isn't going to get solved on here. I'll need to take it for a burn through some crud and most likely find out that I've been exceptionally optimistic.

If that's the case... anyone want to buy a new 25mm tyre?

Who is online

Users browsing this forum: nickobec