CRF250 L thread

[minkyhead]

tough one gearing on the little crf is not easy if your doing roadwork

so i keep trying stuff on the 300s and theyt run really well ....to compare i generally run 15/38 against the crfs 13/40 and it pulls this pretty well ... which indicates how much more braap the 300 unit has . for my spare enduro wheel ive have a 40 rear fitted to allow for the bigger tyre
i can carry a 14 front and change out if needed and it really does bob on on that gearing ...its not that far off me old drz ..has a surprising turn of speed ..but more important its very good in tighter steeper stuff but isnt really viable for long distance over 60mph ...but its a great option to have tucked in the pannier

i have a spare wheel and generally have a different rear sprocket on for the tyre

ive tried a lot and the difference is huge ....

DSC_1096 by minkyhead56, on Flickr

the 120/100 metzlers were a monster tyre and were without doubt the worse road tyre ever made how they got dot approval is a mystery ..5 miles on a dry road and it was off and sold on

the e09 does real well for me im oop north and have a lot of rocky hardpack trails ..its a default travel tyre its 130/80 /18

the metxler is 120/90/18 and i lie that but its a very high sidwall tyre 1500 miles winter tyre and then its handling is pants but its only hallf worn ....

so having run a kenda trackmaster in the balkans a while back similar to the metzler i saw a vee rubber tyre which looks identical ..now the kenda is a big tyre like the metzler and maxxis ITs ...so i though at 40 quid id downsize to a 110/100/18 vee

heres the weird thing its as wide as the 130 e09 and pretty much identical in height ...and thats a good thing when it comes to one off gearing ......

so me latest plan is to run the vee with 15/38 and then if i need to attend a mudfet like slopshire ...i can band the 14 on ....

at the moment me rear sprockets are 15/38 15/40 and 15/41 and the cool thing is thae chain will allow any combo ......my prefered travel option is 15/38 with a option of 14/38 ....so it would be good to get the enduro wheel to pull the same gearing as the e09 ........

cant comment if the vee is as good as the kenda yet ...but its cheap and easy to try with decent reviews ... i like the kenda and i also like the vees profile //very aggresive but no swingarm clearance gearing and height payback ...its mad isnt it the 130 e09 is narrower than the 110 vee rubber ..thats why you can only go so far on gearing calculations you just got to try stuff

130/80.....110/100

IMG_20181202_010155 by minkyhead56, on Flickr


half worn metzler unicross 120/90 vee rubber 110/100


IMG_20181202_010740 by minkyhead56, on Flickr

IMG_20181202_010921 by minkyhead56, on Flickr

[garyboy]

thankyou minky for a comprehensive review of tyres and sizes.
and for the time taken for the explanation and pics.


it goes to show how complex a seemingly simple change is,
.. like tyre size, tyre profile,
.. even without the change in ratios from front/rear sprockets.

it shows just how much research, development, and thought goes into each aspect of motorcycle design, that we dont even realise until we try to change oem std !!

[garyboy]

I did not realise that `simply` changing the aspect ratio of a tyre could have such drastic consequences.

80 to 90 % profile seems such a small an insignificant amount.
but of course, different manufacturers, it seems, use those figures in different ways, as the size of the knobblies will vary, and seem to be additional to the profile????
and the pattern will vary .. some having more side projections .. some more height. ??


Thankyou minky for the heads up on tyre choice
not heard of vee rubber tyres before .. their range looks interesting, for enduro/mx.


I think, as someone on here said, I will stick next time to the oem std sizes of tyres (80% profile)
tho I do like the feel of the unicross 90%
tho it may be different when half worn?

[garyboy]

these are the results I got from minky's `gearing commander`for the crf250L ..

1. with std tyre, (80% profile) percentage decrease in gearing ..

14/40 = 0
14/42 = 5.0
14/45 = 12.5

13/40 = 7.7
13/42 = 13.1
13/45 = 21.2


2. with larger tyre (90%profile) percentage decrease in gearing ..

14/45 = 8.5
13/45 = 16.8
also
14/40 = - 3.6
14/42 = 1.3
and
13/40 = 3.9
13/42 = 9.1

some of these will involve a longer chain!!



generally .. (for same tyre) ..
1 tooth extra at the rear will decrease the gearing by about 2.5% ?
1 tooth less at the front will decrease the gearing by about 7.0% ?
(I think??)

so, if this is right .. 13/42 = 7.0 + 2x2.5 = 12% (13.1 on chart!!) .. so its close!

but tyre manufacturers mess this up !
with their different profile shapes.

.. and by putting a bigger tyre on the rear this will offset drastically the advantage gained in reducing the gearing (as I found out)

[minkyhead]

soo fitted me new wheel thisafter and went for a mini braaaap ... seems ok for a aggressive tyre it wenrt to bad at all particulary new on wet roads .....seems pleanty of tyre for the crf .......sods law has it i got a puncture 2 miles from home .dark and pissing doen of course ...instead of doin the tube i got err indoors out to fetch the spare wheel and me headtorch ...cursing here as the e09s are fitted tubless but decided to use a tube as i wanted to use low pressures with these and the bead wont seal that low

used them little hoses to hold the spacers while i rolled the wheel in on the ugly stick and they worked ace 10 mins job done .....so when fixed the puncture and refitted the wheel at home i took a few pics on me phone .... two short peices either end allow you to get the pin in easy by knocking the inside hose to the centre of the hub without having to line up both sides .. and then knock em out when the exit side is lined up ....works a treat

ace trick for any bike with floppy spacer syndrome ... a couple o bits of hose in the tool tube can deffo save some money in the swear box



IMG_20181202_161313_HHT by minkyhead56, on Flickr

[garyboy]

I think my rear axle goes in from the other side?

is yours reversed?
or mine wrong?

ps
how was the new tyre off road?

[Thedktor]

Gary I think gearing is quite a personal thing and though calculating the results of changes is quite interesting ultimate it comes down to how it feels.

Take my DRZ-E for example, standard gearing is 14-47 and works well off road. On the road its a different story as though the engine revs quite high and will do 80+ it feels very busy even at 50 so most people compromise with 15-47 or 14-44 (roughly the same).

However there is still a lot of revs at 60+, I mean why ride a 400 and be limited to cruising at 55?

So I run 15-44, same as the trail "S" model, and on the road it rips! 70, 80 no problem though its still quite busy and not exactly a motorway cruiser.

Off-road and first is a bit tall now but it will chug along in snotty stuff without needing the clutch.

Now, at the other extreme when I used another DR for enduros I ran 13-47 - quite a difference! Fabulous off-road and it would still howl up to 70mph, but comfortable cruising on the road was 45-50mph, i.e. about the same as a 125!

OK so the DRZ is a specific case with quite a narrow 5-spd box, but the point being its often best to just try things and see what your own personal compromise is between road and off-road gear ratios. And you can have some fun doing it

[garyboy]

yes, Steve, I agree that facts and calculations do not give a real picture of the effects of changes in gear ratios and tyre size.
and that you have to try it out and see how it feels .. especially as our calculations may not give the gearing we really wanted or expected.

I certainly did not expect a slightly oversize tyre to negate the effect of +5t on the rear!

since then I been thinking (and it does hurt a lot) that bikes should have a wider gear range for on/off road .. a bit like a mtb that has a front sprocket gear variable capability. but inside the gear box? .. an extra override cog?



relating to my recent clutch burn out .. I am wondering if the rear tyre rubbing on the swing arm may have caused it???? .. rather than my feathering??????

[Scott_rider]

...don’t know if this has been mentioned but the popular Mitas CO2 rear tyres are mahoosive...regardless of what size it says on the casing

[garyboy]

done around 8000 miles and on third clutch with a new one needed soon

I using Halfords m/c oil

been told it makes the clutch slip and wear out …. doh!!!! ?????

been told to use ..
52651135_243631486523983_901965539004383232_n by gary boy, on Flickr

fully synthetic

comments? obseervations????