Wheel sizes

[Grindle]

I have bought a 1998 Suzuki DR800 single which has had a lot of weight taken out of it so rather than the lardy stock weight of 180kgs dry, it's nearer 155 kgs.
It's still running the original wheels which are 21 front and 18 rear. What downsides if any would there be if i fit a pair of lighter 17s at both ends? 17s mean sticky tyres can be fitted in aggressive widths. The 90/90x 21 front and 130/80 x 18 rear would get swapped for probably 120/70x17 and 160/60 x 17.
Anyone imagine any downsides to doing this for a sporty road single?

Edited by Grindle on Friday 26th April 08:48

[gareth_r]

Do an internet search for DR800 supermoto.

[klootzak]

Back in the 90s I ran a KDX250 with a 16" or 17" front (can't remember exactly). With a fat little road tyre it was much quicker steering than the original 21" on knobblies.

Had road rubber on the OE 18" wheel at the back. Lower profile of the tyre may have affected the gearing a little, but overall the gears were so low anyway it was hard to tell.

k

ETA – no functional downsides but it did look like the bike was running on castors instead of proper wheels.

Edited by klootzak on Friday 26th April 03:56

[Grindle]

It seems a few people have used the DR to make a supermoto and 779cc of single is a good base i guess. The wheels go on today and i't's already got things like lightweight exhaust, smaller/lighter seat and many unnecessary bits removed. A place at Ruddington in Notts. i forget the name rebuilt the motor a year ago and gave it a light tune by gas-flowing the head and 1 or 2 other mods so the engine is kicking out 60 bhp, pretty good for one pot.
60 bhp/150kgs works for me so here come summer!

[Tango13]

The smaller wheels will completely confuse your speedo.