Thorn audax fork - metal at the bottom of steerer inside the fork?

[TheShipwright]

On a Thorn Audax fork and maybe all Thorn forks, what is the metal at the bottom of steerer where meets the inside of the fork crown for?
Is it for attaching a mudguard?
Thanks

[PH]

Yes, direct fitting of a mudguard, the hole is threaded, just drill a hole in the guard and screw it in.  I find a shallow button head and flat washer work well, also if there's clearance a rubber tap washer stops any chance of rattle.

[TheShipwright]

Thanks PH I appreciate the response. I'm trying to squeeze in as large as possible tyres whilst planning for mudguards.

[PH]

It is a good design for that, it's then the brake* rather than the fork or guard that's the limiting factor for tyre size. 
*Assuming rim brake.

[TheShipwright]

I think my brakes are OK as they're Shimano R650's which "look" just about wide enough to accommodate 32mm tyres and guards however I'm sure it will be tighter at the front compared to the rear.

[PH]

I think my brakes are OK as they're Shimano R650's which "look" just about wide enough to accommodate 32mm tyres and guards however I'm sure it will be tighter at the front compared to the rear.

Even with those brakes, on a non Thorn audax bike, I was never happy going above a genuine 30mm, which is what 32mm Pasela's used to measure on Open Pro rims (They may have revised the sizing since) In part it depends on your opinion on what adequate clearance is. There's a photo somewhere on here of a Thorn Audax supplied with what I wouldn't consider enough clearance, though someone at Thorn obviously did, I think that poster made their own mind up and changed the tyres.
On the audax bike, which I no longer have, I used to run 32's at the back and 28's at the front, which worked fine, considering the weight distribution there's good reason to run different sizes, a couple of my current bikes still do, 35/32 and 40/35.

[lewis noble]

Hello PH and Shipwright

I think that 'someone' mentioned in the last PH post was me!!

Yes, I bought a, Audax Mk3R in 2017 I think it was, and specified Marathon Supreme 700 x 32 . . . . .which the brochure said was Ok but a tight fit.  I chose this because I have always had A1 service from Supremes, keen to stick with them.

But the clearances were very tight, too tight in my view.  On country lanes, gravel could be heard scratching its way round the length of the mudguards, and at that time, a big programme of road repairs in Sheffield meant the road surfaces, though improved, were often gravelly if waiting for sweeping / finishing off.  And I also reckoned that although the guards had been fitted very accurately and with great care, minor damage / distortion would be hard to fix on a ride / in the dark.

Without guards, the 32 Supremes would have been fine, brake clearance OK if I remember rightly. 

So I settled on Schwalbe One 700 x 28, which have been fine, decent ride and puncture free - I have retained mudguards.  32 was the smallest size available in the Supremes.

So the 32 Supremes will fit, but in my own personal opinion, were too tight for anything other than excellent clean road surfaces.  To be fair though, I never had a wheel jam, but it felt wrong to me.

Lewis

[lewis noble]

I've found my original thread and photo, with the Audax in original trim and with 32 Supremes / mudguards.  The clearance does look tight. 

My thread "New Audax on way", username lewisjnoble.  Page 2, December 16th dated post.[ http://thorncyclesforum.co.uk/index.php?topic=12712.msg94761#msg94761 -- inserted by Dan.]  And yes, PH's helpful advice on tyres bars and other matters at various stages in that thread.  I did change the bars, to Bontrager compact bars, better for me.  And fitted bar end shifters, again better for my creaking joints, though I prefer using the original STIs. 

I still ride the Audax as bike of choice, Sherpa is on loan to daughter at present. 

Lewis

[lewis noble]

Thanks as always, Dan

Lewis

[TheShipwright]

Thanks Lewis and PH for the input.

It's seems a bit of a minefield getting the tyres, rims and guards correct and to a suitable clearance you're happy with.

I've found that the SKS Longboards profile (rounded) works really well with my R650 brakes as it doesn't foul the brake when applied but still provides plenty of cover.

I'm aiming 32mm Gravel kings (smooth ones) and guards but might have to adopt the idea of 28/30 up front and a 32 at the back for comfort.
99% of my riding is London roads hence the desire to increase rubber size

What's slightly annoying is that the pad holders on the brakes arms aren't bottomed out, I think they've got another few MMs of downward movement, which I could be use for rubber/clearnace!

The bike's great so worth putting in the effort to make it as comfy as possible.