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Interesting (to me) tyre fitment quandary GS400

  • Thread starter Thread starter chugchug
  • Start date Start date
C

chugchug

Guest
Hi there, I own three GS400?s (a stock regular rider, a mild street-tracker project and a parts bike.) I was looking to order some new tyres for my regular rider which is running:

100/90 18 56h rear and a 90/90 18 front.

I was looking at the Avon (RoadRunner) and Bridgestone (BT45) websites (pretty much the only tyres available in the UK) for fitment specs when I noticed that my rims:

1.65 front, 1.85 rear

are undersized according to their minimum rim widths:

1.85 front, 2.15 rear

I looked at my other bikes and they are both running:

4.00 x 18 rears

which I believe is the equivalent to 110mm. The original factory spec is for a:

3 inch front and 3.5 rear

which only seem to covered by Dunlop with their K82 that has a very ?classic? profile.

I am guessing that the tyre manufacturers are a little conservative with their specifications and I understand the problems associated with bead seating when putting a marginally oversized tyre on a narrow rim.
I guess my question is has anybody had any experience of/has heard of an oversize tyre rolling off a rim? Or would they feel comfortable fitting a tyre marginally oversized? Or should I stick rigidly to manufacturer specs and fit the Dunlops and lose the benefits of a more modern profile? All opinions welcome. Cheers.
 
I reckon they're being really conservative!

When I got my 450E (same rim sizes) it had a 90/90-18 on the front and 4.10-18 on the back.

Doing my "scrambler" project I wanted dual sports and the only way I could do it was a Pirelli Scorpion Trail on the front and MT90 A/T on the back.

I ended up with a 100/90-18 on the front and another 4.10-18 on the back. Both were recommended, supplied, and fitted by a bike shop that are supposed to know their stuff. After 6000km's on them I'm lovin' 'em!

I'm not that an extreme rider but they have plenty of grip for me and I don't feel any issues with what's technically an over sized tyre on the front.

I'm almost due for another rear tyre as the dual sport appears quite soft, so probably next time around when the front needs doing I'll be looking at something like the BT45's myself, and I'll be staying with the 100/90-18 front if I can as my Acewell gauge has been calibrated for that size now.
 
I guess 6000km's and a bike shop's recommendation are pretty good indicators as to what works in the real world. I assume that the tyre manufacturers are (quite rightly) covering themselves and erring on the side of caution. Thanks for the input.
 
Yeah more than likely... mind you I definitely wouldn't go any larger than what I have on there now... I reckon that would be more than stretching the friendship...
 
I'll think I'll go with 90/90 18 on the front and 110/80 18 on the rear (roughly 4.00) and see how that pans out. Cheers.
 
Chug, look on eBay for a GN400 front wheel. It is the older snowflake 18" mag, but is 1.85" wide. might open up some possibilities for ya......
 
Hey Big Rich, after cross-referencing the part schematics for GS400/GN400 it turns out that the GN400 mag has a slightly longer axle although it uses the same bearings etc (and is 1.85 wide) cheers anyway.
 
All good man. I'm actually getting a GS450 today that has a GN400 front wheel mounted. Once I start to clean it up, I'll look for any differences, but for the time being I know it at least rolls on it........
 
Big Rich said:
All good man. I'm actually getting a GS450 today that has a GN400 front wheel mounted. Once I start to clean it up, I'll look for any differences, but for the time being I know it at least rolls on it........
Click to expand...

Ooooh it's a goer Rich, nice one! :D
 
There are some other details that go with the story.........I'll let you know by the end of the day though Pete.
 
Big Rich said:
There are some other details that go with the story.........I'll let you know by the end of the day though Pete.
Click to expand...

Looking forward to it Rich :)

I'll be off to bed soon but expect to see some news when I get up in the morning ;)
 
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