A Sprint wheel is a Sprint wheel, right? Or is it?

[Carledo]

Something odd happened to me yesterday, I went to get a new tyre put on one of wheels from my series 1 75 Sprint auto it'd had a tyre fitted without a tube previously that had a damaged bead seal and wouldn't hold air.

So I just dropped off the bare wheel and new tyre and the guy said he'd call me when it was done, fair enough.

So imagine my surprise when he calls me back a bit later and say's this isn't a tubeless rim. Of course it is, I scoff, all Sprint rims are tubeless. But he insists, so I go down for a peek and he's right, there's no sign of the ridges at the inner sides of the bead sealing flats that denote a tubeless rim. Moreover the hole for the valve doesn't look right either. Embarrassing! I have got him to get an appropriate tube and fit it.

Now i've not long had a set of new tyres fitted tubelessly without comment to a late Sprint's wheels and many others over the years and never noticed anything amiss about running tubeless, the couple of odd Sprint wheels I have lurking about both have ridges, 75 and 77 DOM respectively.

So i check the date on this abberation and its not clear but appears to be either 0 73 or 6 73, so a very early one regardless and when I look at all the other wheels on the car they all have tubes fitted (haven't checked their dates yet though i'm assuming they are equally early)

So is this a thing? I've had limited dealings with early cars, did they really enter production with tubed tyres fitted? Anyone else got any early rims without tyres on they can check? It seems to me to be a bit odd, but then Triumph were experimenting with the Sprint on alloys and did several other thing oddly, like the nut design, alloy nuts and no steel inserts in this early wheel either. Maybe they had limited faith in the wheel's ability to hold air when tubeless?

In all my years on this forum i've never noticed it mentioned, is it known by anyone?

Confused of Highley

[TrustNo1]

I've never known any Dolomite or derivative to have tubed tyres but that aside the bigger issue is did your tyre fitted put a tube in a modern tyre as they are not suitable for tubes due to the construction on the inner side walls?
There are two different manufaturers of Sprint Alloy wheels, both of which i fofgrt but I'm sure someone will be along to say, this could be the differing between early and late rim but they will both be J rims which are tubeless type.

[Magenta Auto Sprint]

SM = Sterling Metals and GKN.

I have a 73 rim, I'll have a look at that. A cast alloy rim should be air tight and suitable for tubeless tires.

As far as I know, tubes were fitted to steel wheel rims made in two parts or wire wheels, the joints were not air tight.

My 1942 Jeep has split rims or combat rims (which are bolted together) and they all have tubes for this reason.

[GrahamFountain]

Anyone else got any early rims without tyres on they can check?

I've a spare set of 1973 wheels in the garage with no tires - mebee there's only 3. As I remember, they are all GKN's not the SM ones.

They're a bit buried at the mo. But I have to move some stuff around cos the wife wants the back seat of her car back from the Doly seats I picked up yesterday. So I'll dig them out and post photos then.

Graham

[Carledo]

What i'm particularly interested in, is the presence or absence of the raised ridges that are there to stop the tyre beads slipping in when the tyre is deflated. No rim that is designed as tubeless should be without these ridges, whatever the material or construction, it's an essential safety factor in the design.

Starting in the motor trade in 1970 as I did, one of the first things I became aware of was this difference, as first year apprentices traditionally "fix punctures and make tea" and little else, in terms of practical work. I was no exception! In those days, tubed (crossply) tyres were still very much the norm and few cars had tubeless tyres. But I learnt to dread these because the garage's ancient and totally unpowered tyre changing rig made VERY hard work of busting tubeless bead seals!

I've come across tubed type rims made well into the 90s, though mostly for trailer or caravan use. Most Triumph Herald wheels made in the 60s were made for tubed tyres, to name but one model.

I'm aware of the different manufacture names of Sprint alloys, but i'm led to believe they are both divisions of the same parent company. Like so much else, this could be another myth! I'm willing to be corrected. In the meantime, if the rain stops long enough I need to do some more research on the rims I have here in terms of date and manufacture. The one I know absolutely is like this, is dated 73, but that seems rather early to be OE for my late 75 registered series 1 car with it's VA 10xxx+ comm number. A retrofit perhaps?

Steve

[GrahamFountain]

I've dug them out. There's 3 x 73 GKNs, 1 x 77 GKN, and 1 x 76 SM. There is a difference in the legend, so it's not entirely a myth or, one might even say, legendary.

I can't see any undercut or raised rim inside any of the rim edges, and all but the SM have valve inserts. I might find a GKN that's been ornamenting the garden for a bit, with no insert.

I'll photograph them when I've recovered from all that shoving stuff around and had me tea. The new seats are nice.

Graham

[GrahamFountain]

The first is of the 73 GKN wheel. The others are all of what I take to be the SM one. Even the purely ornamental wheels have valve inserts.















Hope that's what you were looking for Steve.

Grsham