Front Tyre size

In the build of my Triton, using 60's Dommi bits, I have just gone to install my new replica 1966 style front mudguard and realise the I do not have sufficient width clearance with the TT100 4.10 19 tyre.
I now realise that the original tyre called for was a 3.00 or 3.25 19, which translates to a modern TT100 3.60 19.
According to my measurement the reduction of the width from 100 mm to 90 mm should be sufficient, but has anybody had any real life experience of this?
Thanks for any responses. Leon

I used 4.10 TT100 on the front of my Dunstall Atlas, all I did was use bigger Y piece and longer mudguard stays.

Thanks Berhard. The issue is that the 66 type guard has only about 100 mm internal gap and the 4.10 is an interference fit. I would like to have it sitting in the correct position and not raise it.
Before I purchase and fit a 3.60 19 which is supposedly 90 mm, I would like to see if it has worked for someone else.

If it helps, I run a 3.60 19 TT100 on the front of a stock 1964 650SS. By memory, I found that a 4.10 seemed an awfully tight fit, especially considering the tyre could "grow" at speed. Bear in mind that pre 1964 forks are slightly closer together than 1964 on, which I assume would make a 4.10 even more problematic. My bike steers fine with a 3.60 - at least to the limit of my modest abilities.

Thanks Bodger, exactly what I was wanting to hear. My forks are the later type, so it should all be the same as your experience. Cheers Leon

Bodger said:

If it helps, I run a 3.60 19 TT100 on the front of a stock 1964 650SS. By memory, I found that a 4.10 seemed an awfully tight fit, especially considering the tyre could "grow" at speed. Bear in mind that pre 1964 forks are slightly closer together than 1964 on, which I assume would make a 4.10 even more problematic. My bike steers fine with a 3.60 - at least to the limit of my modest abilities.

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Up till the Atlas, the Domi forks were 7in between centres, my ’65 Atlas had forks that were 73/8 inch between centres it will therefore be a tight squeeze on the narrower forks.

I also fitted a Alloy mudguard which are readily available.

leonc,3/60/19 is the size you need, chris.

Put a 3.60 19 on today, lots of clearance, perfect, thank you gentlemen.

Just to confirm your choice, I found an original Dunlop front rim rim with a 3.60 - 19 tyre in the shed today. It's off a 1962 single carb Atlas rolling basket case. The tyre is marked, "Dunlop Roadmaster - K81." The tyre certainly has enough cracks in it to be original. Also, FWIW, I believe that the switch to slightly wider yokes and slightly further apart stanchions occurred in 1964 and is marked by inclusion of the steering lock in the top yoke. What I have never figured out is whether the width of the front fender and upper fender brace changed. I suspect that the brace was just forced to fit, but I'm not certain. I've been told the full valance fender got wider, but I don't know if that is true.

After my brain woke up realised the tyre on my 1962 Atlas rim can't be the tyre that originally came with the bike since K81's did not come out until 1968. Oh well, but it is the right size tyre for the bike.

Bodger said:

. What I have never figured out is whether the width of the front fender and upper fender brace changed. I suspect that the brace was just forced to fit, but I'm not certain. I've been told the full valance fender got wider, but I don't know if that is true.

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I would say the fender got wider, I tried to fit a 7 3/8 Atlas fender into a 7 inch top yolk and it couldn’t be done.