Race reports

**Sketchy_Racer** · 30th June 2006, 16:59

Originally Posted by texmo

1kg is suposed to work out to 1hp in theroy I am told

sounds rubbish to me.

lets say - a 30hp bike with a 50 kg rider and a 100kg bike

so thats a rolling 150kg which equates to 5kg per 1 Hp

now a 50hp bike weighing 180kg and a 70kg rider

= 250kg rolling. which equals also 5kg per 1hp.

so the lighter bike will have a better launce, as there is less mass to accelerate, but when wind factors come into it, the heavyer bikes 20 more hp will piss all over the light bike.

and as you only launch once in a race, then the big bike will have the advantage

the fact I wont take my bike past 16,000rmp

wouldn't think they would make any power past that anyways?? i know my cbr flatted out at 15000..... dunno bout the ZXRs though...

**texmo** · 30th June 2006, 21:47

yeap ok... See you at the next meet then.

**Sketchy_Racer** · 30th June 2006, 22:03

yer..

The

stops when the flag drops

**Motoracer** · 30th June 2006, 23:53

Originally Posted by texmo

Its a pritty big debate but 1kg is suposed to work out to 1hp in theroy I am told. I am getting to about 160ish and the straights I think dunno what you guys are getting I also have more tourqe. There is a diffrence but by the time you take into account my fat arse and the fact I wont take my bike past 16,000rmp the gaps not so big.

You'r not fat! It's just your leathers that make your arse look big.

**N4CR** · 30th June 2006, 23:57

Originally Posted by RG100!!

Also 150 has about 25bhp wheras the 250s are supposed to be about 40bhp??

Our 'chunky' 250's are about 35ps on average at the rear wheel. 45ps crank but if they are getting 35~ps when they are averagely tuned i'd say i'ts a little over 45ps crank with a pipe and good tuning...

edit: 160kg wet (measured it myself..) for the C model zxr like texmo's and mine.

**vtec** · 1st July 2006, 00:42

Originally Posted by RG100!!

No.... it is still a big difference.... because once you get to 100kph + you have wind effect. weight doesn't matter so much.... but power does.

Also 150 has about 25bhp wheras the 250s are supposed to be about 40bhp??

Well, Neil was telling me that his RG150 has a dyno'd at the wheel figure of 32RWHP (Rear wheel Horsepower). Now, I'm pretty sure that a standard 250 4 stroke from the early 90's has close to 45HP at the Crank, but as N4CR says, they've got about 36hp at the wheels. And since we are all running in StreetStock I'm pretty sure that we have stock bikes. I'll take my tank off and show you my standard intake and everything. Standard pipe etc. I'd like to dynotest my CBR250 to see what it's got at the wheels, but I'm just not willing to pay any money for something I don't need to do.

Also I think my CBR is about 153kg dry, and the RG's are about 128 wet (I think). but I only weigh about 67kg, so the weight differences between me and Neil on the bikes isn't very much, seeing as he's about 90kg. So the horsepower difference is much more noticeable. Still I'd rather be on a 4stroke any day.

These figures also don't take into account the shape and usability of the power curve. The powercurve on the 4stroke is much smoother, and it's pretty fucken good as long as you keep it between 12,000 and 18,000rpm. So I'd say it's easier to ride, and has better power output for longer periods than the two stroke. A really top notch rider with correct gearing can probably keep an RG in a good rev range most of the time, and negate much of the smooth curve advantage that the 4strokes have.

Another point, although the 4strokes have the power/speed advantage, I do believe that the RG's are better behaved in the wet. In the dry, I'm untouchable, but in the wet I really have to work my arse off to beat big Neil on his RG150. I think the thinner tyres give a more sure footed feel than wider tyres in the wet, and are much less likely to aquaplane. Some people say lowering tyre pressure is good for cold conditions to get tyre temperature up, (which is what I did at the last race meeting, and was sliding everywhere), but I've also heard that high pressure is good, cause it gives you a smaller contact patch with more pressure in the smaller patch, meaning less likely to aquaplane, or a more sure footed feel in the wet. Depends how wet though. If it's just damp, I think the 4stroke gets it's advantage back, but if it's puddle wet, the 2strokers can really make better headway.

I realise this is Texmo's race report thread, but I think this is topical, because a few of us have had a fair bit of discussion about it, and my opinion is not necessarily shared by ANYONE else. But I've put a lot of thought into it, and have come to the conclusion that I like riding my 4stroke.

Can't wait to see your progress at the next round Texmo. And RG? If you're that bothered, then bring your CBR250R along, show us your magic on that.

**k14** · 1st July 2006, 01:05

Originally Posted by vtec

Some people say lowering tyre pressure is good for cold conditions to get tyre temperature up, (which is what I did at the last race meeting, and was sliding everywhere), but I've also heard that high pressure is good, cause it gives you a smaller contact patch with more pressure in the smaller patch, meaning less likely to aquaplane, or a more sure footed feel in the wet.

From what I've been told you run a few psi higher in the wet to help open up the grooves a bit more and get a better contact patch. Seems to make sense too. In the wet most of the time you've got 2/3rds of fuckall heat in the tyres anyway so they are having to work at fairly close to ambient temperatures anyway.

**Sketchy_Racer** · 1st July 2006, 09:25

Originally Posted by Vtec

And RG? If you're that bothered, then bring your CBR250R along, show us your magic on that.

would love to, but it is non existent....

still havnt changed the bike list....

your right in saying the four stroke has the advantage....

having ridden the CBR 250 mc22 and mc19 and the RG 150 and a good ZXR250...

I would have the mc22 any day of the week.

they are head and shoulders over the 150....

I think you should ride a 150 before you assume it has a bigger wet weather advantage.

i think the RG150s suck compared to the mc22s . the RGs flex like hell and have a rear shock that is about as good as a pogo stick.... well not that bad... but they are not good either.....

one day ill borrow my mates mc22 to race..... would be interesting to see where i come on it.

RG's are about 128 wet

I stand corrected.

**vtec** · 1st July 2006, 10:20

How much do they weigh RG?

**Sketchy_Racer** · 1st July 2006, 10:37

err sorry...

i just went and weighed my KRR150.... thats 126.5 kg. dry.

so yeah the RGs prob arn't to far off that....

**vtec** · 1st July 2006, 10:40

Cool thanks for checking RG.
Have you got no fluids in your KR at the moment?

**Sketchy_Racer** · 1st July 2006, 12:12

nope.... well i do now... but no before..

just did a gear box oil change- so there was none and no 2stroke oil or petrol in there either (its always on empty)

but i didn't have the radiator water or brake fluid etc out

**vtec** · 1st July 2006, 13:05

Yeah that's close enough to dry for me, there would only be a couple of kilo of water in the radiator, and brake fluid would be negligible... so there's about a 30kilo difference between the 4 strokes and 2 strokes. And on some of the tuned 2 strokes, the power is quite close. But on others, they're probably a bit down on Neil's 32rwhp. So I think approx 5-8rwhp difference between the 2strokes and 4 strokes.