Alez
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| posted on 13/7/05 at 03:24 PM |
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Increasing wheel diameter
My Fireblade now has 185/60R13 soft tyres. This is truly great for city and track, reaches 110 mph at 11000 rpm. I have been traveling with them,
usually doing steady 80 mph at about 8000 rpm. I'm considering buying a set of cheap bigger wheels for journeys only. That way I don't need
to travel on slicks (somewhat stupid) plus I lower my steady rpms.
I was thinking something like 80 mph at about 7000 rpm. The reason for this choice is that both 80 mph and 7000 rpm look like reasonable figures for
steady highway cruising.
My problem is that the resulting wheel sizes are somewhat huge compared to the original. Also these bigger diameter wheels usually come in wider
footprints only. I can see how any benefit in fuel consumpion associated to dropping rpms is then compensated by an increased overall weight of the
car plus increased wheel footprint. Still I think it may be good for engine wear, what do you think?
So my question is: am I going too big? Should I go for smaller wheels, say 7500 rpm at 80 mph or something? Or is my choice of 7000 rpm at 80 mph a
sensible one?
My choice of 7000 rpm at 80 mph gives the results in the attached pic (lousy Excel calc). I don't know which of these exist and which are common
(ie cheap), obviously the resulting profiles need to be rounded in steps of 5.
Comments?
Cheers,
Alex
PS: the wheels fit nicely in the arches, that's not a problem 
 
Rescued attachment tyres.jpg
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andy d (rizla)
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| posted on 13/7/05 at 07:36 PM |
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hi i have 195 55 15 wheels with a 3.62-1 diff this gives about 6500 rpm at 80
and still sub 4 seconds on acceleration
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smart51
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| posted on 13/7/05 at 09:20 PM |
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195 50 15 tyres tend to be a bit cheaper than 195 55 or 195 45
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Alez
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| posted on 14/7/05 at 08:32 AM |
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The overall diameter of Andy's tyres is 596 mm and the resulting gearing is longer than mine by A LOT (he gets 6500 rpm where I'm getting
8000!!). So the rpm figures I was considering are not stupid, it's just I may need to think about changing my diff ratio 
BTW Andy, have you actually MEASURED sub-4 secs with a standard Fireblade engine and those ratios? It sounds like a very good figure, how much does
your car weigh? What's your diff (open / LSD) and rear suspension setup? Road tyres or slicks?
Cheers,
Alex
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andy d (rizla)
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| posted on 14/7/05 at 06:39 PM |
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real figures are,on yokahama road tyres,0-60 3.7 seconds(timed at tuning japanese after rolling road tune) top speed 137.4mph(gps timed at the sme
company)
the diff is open,no lsd(as this causes drag)
total weight of car at test 418kg wet
suspention is double wishbone with protech shocks all round
and in the words of ian hyne(kitcar magazine) "the gearing on this car is spot on,the gear changes come in equal lunges up the box "
hope that helps
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ChrisGamlin
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| posted on 14/7/05 at 06:46 PM |
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Andy, is that Tuning Japanese in Aldershot? If so would you recommend them as they are local to me and i'll need to get mine on the rollers
soon.
How did they measure the accceleration / speeds, on the rollers?
Chris
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andy d (rizla)
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| posted on 14/7/05 at 07:31 PM |
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not mesured on the rollers i had it tested after the tuning session on private road
yes highly recomend them,the man you need to speek to is paul
they aint cheep thow my session including a dyno jet kit was not far short of £500
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ChrisGamlin
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| posted on 14/7/05 at 07:44 PM |
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Ouch  how come it was so much, thats ~£400 labour so it must have taken them an especially long time on the rollers or something?
Im also concerned that although they sell Dynojets, Im not sure how well they know Power Commanders for FI bikes, so I think PDQ in Slough might be a
better bet if TJ are that expensive too.
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andy d (rizla)
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| posted on 14/7/05 at 08:03 PM |
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they had the car for a week,not to work on for that long,just i could only drop off and pick up on a saturday
as the name sugests they specialize in jap engines,car and bike
they know all about power comanders and that
but as isaid very dear
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ChrisGamlin
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| posted on 14/7/05 at 08:46 PM |
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Sounds like they might have charged you storage too
I'll give TJ a call to see how much it will but what youve said has put me off a little, there's another one nearby,
surreyrollingroad.co.uk in Camberley so I might give them a call too.
cheers
Chris
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Alez
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| posted on 15/7/05 at 07:31 AM |
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Cheers Andy, I'm very impressed, What is your engine?? Fireblade? What year? Tuned or standard?
I'm very impressed really!
Also I wonder why my car weighs 460 kg wet and yours is a mere 418.. I don't think yours can have a lot less stuff than mine, I have nothing
there
Congrats, your little car is a winner!!
Cheers,
Alex
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andy d (rizla)
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| posted on 15/7/05 at 05:41 PM |
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wieght,well thats MNR for you,as to engine its a 1997 rrv fireblade with a pipercross filter and a stage 2 dyno-jet kit,thats it apart from that its
standard
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Alez
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| posted on 18/7/05 at 06:47 AM |
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Congrats!! Fantastic figures, I have the same engine ('97) although I know nothing about dyno jets.. one more thing to learn sometime in the
future..
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