Tyre Price

https://tyretectrading.co.uk/tyres/avon-av92-cobra-chrome-200-50r17-75h-tl-rear-motorcycle-tyre/ £169

 

£235 sounds excessive, what size are your tyres? Doing detective work on your postings about a Thunderbirsd 1700 and looking online, they seem to use 200/50R17 which are £169 from the place I always use. (Plus £7.50 delivery)

The prices have gone up a lot though. My rear 150/80R16 was was £119 a year ago and it's currently £150 so a 26% increase.

 

They are a lot more expensive, but unless I'm missing something, they're £200 from TyreTec.

 

I would check your Triumph booklet mate. I think the previous owner may have put a 55 on but I believe standard is a 200/50 R17, so then the choice is yours

 

I just payed € 420/USD 423/GBP 355 for a complete exchange of the tyres of my Honda NT-1100. For the T120 I payed € 350/USD 353/GBP 296 two weeks ago. The Honda got Continental Road Attack 4 and the T120 Bridgestone BT-46.

 

Unless the computer uses the front wheel's ABS ring for determining speed.

EDIT: Bike in question is old enough to maybe have optional ABS? If so, possibly has another means of determining road speed. Though on another forum someone with same bike (I think) had problem with ABS warning light coming on and speedo not working, so that implies they are connected.

I make it just over 3%. The radius of 17 inch wheel is 216mm so radius with 'proper' tyre is 216mm + 100mm = 316mm. The new 55% ratio tyre would increase that to 326mm and 326/316 ≈ 1.032 or 3.2% more.