38/12.5/16 speed on speedo

[mentalmoshio sophs V8i]

235/70/16 to 750r16 is 10 percent increase

so every 2 inches is 10 percent increase speed

30inch to 38 inch is 40 percent

so 100mph on speedo is 140mph actual speed put simply

i cant change the speedo cause runs on 235/70/16 for road use

[redhand]

Don't think so as a 33" tire will only give you a 14% increase in speed.
Oh and 235/70/16 = 29" diameter.

[mobi]

when i put 31/1050/15 (30.3ish) on the speedo was spot on (the road tyres 235/70/16 was under) and now with 255/85/16 (33") i'm 5 mph over, so 30 on the speedo is 35mph

[clbarclay]

235/70/16 to 750r16 is 10 percent increase

so every 2 inches is 10 percent increase speed

30inch to 38 inch is 40 percent

so 100mph on speedo is 140mph actual speed put simply

i cant change the speedo cause runs on 235/70/16 for road use

Hmm, how long since you did O levels or GCSEs?

A 10% increase (not necisserily 2") in size gives a 10% increse in speed.

Also a 235/70R16 is only 29" high so its a 3" increase to a 7.50R16.


Anyway back to the point, 38/29*100=131% increase. Therefore when driving at 70mph your speedo will actually read 53mph or when speedo reads 70mph your actual speed will be 92 mph


One option is to get a digital bike speedo which can be easily calibrated and run of a front output of the transpherebox. You can then have this speedo displaying the correct speed whilst on bigger tyres and use the factory speedo whilst on standard size tyres.

[mentalmoshio sophs V8i]

the 10 percent was to be always under the speed limit . how many of u have got speeding tickets for being over by just 3 mph its easy done .
if a wanted a true reading i  would just us a road angel for a true reading but im not buying one.

i thought 255/65/16 had the same speedo reading if u had 30/9.5/15 or the following sizes

6oor16

650r16

215/80/16

205r16

225/75/16

235/70/16

with different amouts of tread that varies it a bit as well. your see what i mean by standing

a 235/85/16 road tyre next to a 235/85/16 bronco grizzly claw it will show u what i mean.

[redhand]

the 10 percent was to be always under the speed limit . how many of u have got speeding tickets for being over by just 3 mph its easy done .
if a wanted a true reading i  would just us a road angel for a true reading but im not buying one.

Get a PocketPC with gps then you can have TomTom to tell you how fast your going, what speed you should be going and when your approaching a speed camera or accident blackspot. Never get done for speeding then.

And you can have memory map for when your greenlaning

[mentalmoshio sophs V8i]

if i wanted to have that info .i could just use a bike trip sensor on the front wheel  and computer bit in the cab . greenlaning is not for me

[mentalmoshio sophs V8i]

wrote is bit in the wrong section