Wheel Hub dimensions

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JimCrawford
Posts: 74

Wheel Hub dimensions

Postby JimCrawford » Wed Mar 04, 2020 11:23 am

I've been making up some wheel hubs to be able to change my Nipper from the 3 1/2 x 4.95 tyres (made from unobtainium) to easily obtained and much, much cheaper 4.00 x 4 (even from Tost!). However I've come across an interesting issue regarding the hub sizes which I hope the forum may be able to solve:
The optional, original manufacture, Nipper 4.00 x 4 hub is 75mm between the side plates at the point where the tyre sits in the hub. That is an internal measurement between the side plates. However I have measured the same dimension on a Tost hub and it is much narrower at 45mm.
I have emailed Tost asking them about the recommended mounting width for their tyres and had no response so I am asking the forum if anybody knows the factors which determine the tyre mounting width. I'm inclined to go for 45mm as that's what I've measured on a Tost hub with a Tost tyre as used on my glider.

Regards

Jim

G-ARBG
Posts: 152

Re: Wheel Hub dimensions

Postby G-ARBG » Wed Apr 01, 2020 3:55 pm

Jim,
I've been using Toste 400x 4 tyres on Slingsby 4 inch wheels until recently. At 75mm the wheels fit the standard Nipper axle and the Toste tyres also fit and have performed quite satisfactorily.
R.
G-ARBG

JimCrawford
Posts: 74

Re: Wheel Hub dimensions

Postby JimCrawford » Wed Apr 08, 2020 11:02 am

Hi David,
Thanks for your reply.

I think I'll go for the narrower 45mm hubs. This is based almost entirely on the fact that my glider (LS4), with minimal suspension, uses a single standard Tost 45mm hub which handles even my landings at 427kg AUW, so a Nipper with suspension, two wheels and 340kg AUW should be no problem.
A secondary reason is that with the centre line of the wheel in the same place as the normal 'wide' hub, there is a little extra space (~15mm) between the wheel and the U/C structure to fit a bicycle disc brake caliper.
I'm making the hubs to accept standard (Rohloff) pattern discs, although I think the normal six bolt pattern will also fit - but maybe only with the narrower hubs.
I still don't understand the significance of the variation in hub width. Confused as always.

Jim

JimCrawford
Posts: 74

Re: Wheel Hub dimensions

Postby JimCrawford » Sat Apr 11, 2020 9:23 pm

Correction to post above.
The standard 6 bolt bike disc will not fit as the bolt pcd is too small and interferes with the bearing housing. Rohloff discs have a larger pcd which interferes neither with the bearing housing, nor the central tube separating the flanges. The 160mm diameter bike disc is within a gnats whisker of the Nipper disc and will actually work with the Nipper calipers. I'm only changing to bike calipers because my originals are not serviceable.

Jim

Paul1954
Posts: 15
Location: Norfolk

Re: Wheel Hub dimensions

Postby Paul1954 » Mon May 04, 2020 11:18 am

Hi Jim,

It has been a while, but I remember having new wheels made for one of my Nippers when I couldn’t get replacement 3-1/2 x 4.95 tyres. Brakes were of the original style and I had a similar issue with interference, so compared with my other Nipper with the 400 x 4 wheels, and noticed that there was an alloy spacer fitted between the wheel and the inner stop of the axle. The spacer made up for the smaller wheel hub diameter.

Memory a bit weak after all these years, but the 3-1/2 x 4.95 wheel may also of had a spacer too, but that was thinner?

P.

JimCrawford
Posts: 74

Re: Wheel Hub dimensions

Postby JimCrawford » Mon May 11, 2020 2:31 pm

Hi Paul,

I've measured the spacer on the axle for the 3-1/2 x 4.95 hub and tyre and it is ~ 4.5mm wide. Using a 45mm wide hub placed so the centre of the wheel is in the same place on the axle as the 75mm hub to keep the bending similar, I gain 15mm each side of the hub. Maybe not so much at the radius of the disc caliper as the tyre is starting to bulge out at that point, but I expect to gain 10mm. Playing with some bike calipers gives me confidence that the single action cable operated ones will fit. I'm not so sure about the double action hydraulic units which may be thicker, so I'll stick with cable operation for now.

Jim


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