OzVMX Forum
Clubroom => Bike Talk => Topic started by: lms6201 on June 07, 2008, 06:01:53 am
-
something i,ve always just guessed my way around , but would anyone have a good base formula for things like fr/rear hard surface /soft ? any thoughts appreciated , like does more pressure stick the tread in deeper when it,s wet/soft or is it better to let the tyre spread over
-
13 front 13 rear and ajust from yjere if neccessary
-
I just make sure I blame incorrect pressure too hard or too soft when I fall off, sounds a whole lot better than I can't ride any good.
-
I think 10-18 is a good mark for anything specially on loamy or soft stuff, any less and you need to check you rear has a good tube lock, and totally unscrew your valve retainers.
IF its hard packed or you want to brake traction on corners you can keep uping as far as you like on the rear up into the 20 somthings, although i would keep the front under 20 unless you only had only long corners to run.
Also JUmps if they are ski jumps you might want to keep pressure in them both so you dont pinch a tube, you can always ride slower but if you got a flat you aint riding no where.
-
I think it can change with different tyres and dirt conditions.
-
13-13 dry 11-11 mud, mind you I do occasionaly rip valves out of tubes ::)
-
i used 13 13 for years and found the grip ideal and predictable but after a few flats, and i hate flats, i now run 15 15.
big change hey...
-
Wet = less pressure.
Rocky/hard = higher pressure.
The compromises aren't hard to work out:
Less pressure means less stability, increased chance of ripping out valves (Rossco will be delighted when I inform him of the new-fangled invention called a 'rim-lock'...;D ), more traction on soft/uneven surfaces, better clearing of the tread in mud, greater chance of a pinch-flat.
For racing, I start with around 13~14psi F&R and then adjust to suit. I never go below 10psi, and never above 18psi...
Trail-riding, I tend to add a bit more pressure because I feel that the small-but-definite reduction in traction is worth the extra puncture resistance.
I usually run more pressure on the short travel bikes for much the same reason. Maybe I should spend some money on suspension...
-
So vandy you need to change your tag to " Flat bikie "
-
i'll pay that one freaky!
:D
-
heres my input been racing mx off and on
for 30 years
always ran 13 psi nearly everywhere
10 psi in the mud
never had flats using standard tubes
in the bush 15 psi or less if using hd tubes ;D ;D
-
By and large I run 12-14. Sometimes if it's wet I'll drop the rear to maybe 11-12, but that's about the only time I change it. Can't say I've ever noticed the difference between 12-15, it's really only when I get up above 15 or below 12 that anything becomes noticeable. Maybe I'm just not sensitive enough, but I reckon anything around 12-14 will work just fine.
-
I normally whack in 20lb front and rear before I leave and then when I get to the track and see what it's like I bleed out the excess pressure. Same as Graeme, I 'normally' run about 12lb. Have been known to run down to 7lb on the rear but that was with a low profile 6 ply tyre. Pieces of old inner tube slipped through under the tube and out each side onto the beads will do away with the need for those pesky pain in the arse rim locks or 'sun rim' type rim screws. Never had a tyre creep using this method and the 400 is a good test as it destroys tyres if you feel that way inclined. The guy who told me to try it was an ol' speedway sidecar racer (Vincent 1000) and he'd run next to no pressure on the biggest muther tyre you'd seen in all your born natural and all without any rim creep whatsoever.
-
I was told the tyres these days need a bit more pressure to work properly so i run 16 psi. I dont like the tyre flexing on the rim either. If its muddy i take my ball and go home!Oh except if its cd5... or 6 ;D
-
on a related note, what do you guys use for rim tape? is normal duct tape/wide electrical tape ok?
-
Yes. I find that its far more durable, and makes the rim-lock(s) easier to deal with.
If you use electrical tape, make sure you use good quality stuff (most of the cheap tape isn't very sticky. I like the Nitto brand), and wrap it around the rim at least three times.
-
I was always told as a child (from a champion) 10&12. Depends on your body weight of course, If the the track is dry and hard, increase by 1-2, if you are on adventure trail, then you can afford to go 1PSI more. Tyres are tyres, in the heat, they are soft, in winter they aren't going to budge much for the lighter crew anyway. Rimlocks, tapes and spokes are equally (if not more) as important to the tire pressures.
Mainline, since we are in VMX world, I personally would prefer new rubber. Duct tape is good for race ready, but, will surely just leave a residue for the next owner/restorer???
-
heres my input been racing mx off and on
for 30 years
always ran 13 psi nearly everywhere
10 psi in the mud
never had flats using standard tubes
in the bush 15 psi or less if using hd tubes ;D ;D
I think your on the money holeshot... The pro's seem to use what you run, so if its works for them.. its definately going to be in the ball park for slow me ;D
I run Michellin Heavy duty tubes that are 4mm thick rubber for MX and Enduro, i reckon you could do without the tyre and just run the tube they are that good!!
-
Re the tyre pressure. Ask the guy parked next to you in the pits what he reckons and you'll end up pretty close to the money. I think
-
tyre and tube weight are also worth consideration when playing with wheels and I normally go for the lightest setup I can find. Run a few strips of rubber across the rim instead of rimlocks will also help shed some weight. The lighter the better and if you also run alloy rear sprocket the difference can quite considerable. A lot of suzuki hubs (not sure with other marques) and backing plates are already magnesium but you can still find excess weight in the sprocket bolts, brake cam, brake shoes and such, these can be drilled, hollowed or replaced with hi tensile alloy jobs if you have some spare cash burning a hole in you pocket or happen to have access to aircraft type fasteners ;) it's not a HP gain and it can't really be seen but will make you bike handle better and is definately worth the effort..food for thought..
-
yep , unsprung weight is always an important factor , getting back to tyre pressure , all the replies are very useful info , and all opinions seem to fall into a similar range , it,ll get me into a better idea of what to try , it,s hard when your a bit on your own to get these idea,s like i have just found rimlocks that work , the rubber ones just fold up , am now using the ally with rubber back ones with great results , and they are a lower profile , great result = more than 15 minutes tube life , what,s the dunlop tyre people are using on the frount that hangs on in moist conditions