Author Topic: Road racers rake and trail numbers, tree offsets, etc  (Read 1490 times)

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Offline livefast_dieold

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Re: Road racers rake and trail numbers, tree offsets, etc
« Reply #25 on: April 08, 2019, 02:43:08 pm »
I'm usually using a 15 teeth sprocket! I've bolted a plastic slider on the swingarm, and it doesn't show any particular sign of wear. I've been using this sprocket for the past 3 seasons.

As for the software, it costs 99 € for a lifelong license (https://motochassis.com/product/motorcycle-setup-software/). It covers probably too much stuff for the sake of comparison, maybe there is a free to use software (or something we can do with an excel spreadsheet) to compare our numbers more easily. I found the attached spreadsheet that easily calculates trail, maybe we can extend it furthermore. If someone has already some formulas that he uses to calculate its frame parameters I can update it myself, so we all use the same approach.

You must be winding the absolute piss out of that engine! I run anywhere from 17/44 to 17/48, or a ratio of 2.59 to 2.82, while yours is in the 2.93 range. Must be very short tracks where you race or you are running to 12-13K RPM.

sorry I remembered wrong, it's 16 teeth sprocket! Thanks to have pointed out the nonsense...

Offline grcamna2

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Re: Road racers rake and trail numbers, tree offsets, etc
« Reply #26 on: June 28, 2020, 06:57:09 pm »
subscribed
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S',1982' Suz. GS450TXZ
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline johno

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Re: Road racers rake and trail numbers, tree offsets, etc
« Reply #27 on: June 29, 2020, 07:28:08 pm »
Hi George,
Everyone is pretty focussed on the technical side but don't forget the human side. The technical specs are easy to change, the riding style is more difficult to change. In my very humble and limited road racing experience ( 12th in Aust TT on cb750) when tuning my customers bikes at the track I ended up spending more time tuning the rider than the bike.  In order to bring out the best of the rider I used to leave the stop watch in the car, then make them do laps until they were bored, then adjust the tyre pressures front and back etc without them knowing what I done and asking for feedback from them until they could consistently tell me which way the the pressures made the bike handle. At that point they are ready to start tuning the suspension.
What I think is very important is.......different riders come into the sport from differing backgrounds, ie motocross, speedway or the road and they develop their riding styles accordingly, ie late braking slow cornering, drifting through corners, back the bike in arse first using various techniques. This is a critical point so after I have the rider predicting the tyre pressure thingy the next step is I make adjustable engine mounts to move the engine mass around to see what the rider feels most comfortable with. The engine mass makes the single biggest difference to the bikes handling, all the other factors ie rake , trail etc are fine tuning a bike that was mass produced to suit all.  This process really gets the bike to suit the style of rider and gives them the confidence to embark on the process of fine tuning.
Interestingly for me was after all that dicking around the bike often ended up technically similar to other bikes in the paddock, but with a rider that was much quicker than before.
GRASSHOPPER SOHC HONDAS ARE THE MEANING OF LIFE.

Offline grcamna2

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Re: Road racers rake and trail numbers, tree offsets, etc
« Reply #28 on: June 29, 2020, 07:31:27 pm »
Excellent  :)
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S',1982' Suz. GS450TXZ
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline bear

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Re: Road racers rake and trail numbers, tree offsets, etc
« Reply #29 on: June 30, 2020, 06:45:51 pm »
John,
I didn't realise you had a RR background as well.
A good post and some worthwhile insights for anybody trying to setup from scratch.
You are also spot on regarding a riders history influencing his RR style it can have a big impact on setup.

Cheers,
Brian
The older I get the faster I was.

Offline johno

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Re: Road racers rake and trail numbers, tree offsets, etc
« Reply #30 on: July 01, 2020, 12:31:58 am »
 Cheers Bear,
yeh I didn't explain the point so well, not easy in a quick impromptu posting  :o. What I should have said was let the rider know and experience understeer and oversteer by moving the engine. Once they get their heads around that they take to fine tuning like a duck to water.

Re the RR, without dribbling on too much that occasion was my lucky day and makes a good yarn, 60 plus bikes, two heats of 30 + with top 12 from each heat into final of 24, I got 12th in my heat so just scrapped in, organisers stuffed up the grid draw and I was on second row sitting behind the two Works Team Kawasaki 750's of Greg Hansford and Murray Style and Bill Horseman's on works Suzy 500.  Me on my production K2 bike looking at my Dunlop K81 front tyre then staring at the biggest 3 racing slicks I had ever seen in my life, the famous Ozzy starter Glen Dix walked over to me, tapped me on the helmet and said " are you supposed to be here" I said hell yeh  :D.    I wobbled around , got lapped, hit off the track by Bill Horseman  but kept on going, Bill who post race came over and apologised saying I was like a mobile chicane and he couldn't resist.
Wouldn't you believe it most people blew up or fell off and I ended up 12th on a production bike. Best day of my short riding career,  It came to pass that I was more suited for throwing tools around than riding  ;)
GRASSHOPPER SOHC HONDAS ARE THE MEANING OF LIFE.

Offline johno

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Re: Road racers rake and trail numbers, tree offsets, etc
« Reply #31 on: July 01, 2020, 02:34:59 am »
Right Bear,  talking of understeer and oversteer and what makes it happen, lets talk chairs and see if were on the same page.
It seemed to me that most young blokes at school never got there heads into physics, more likely sport or girls  8). BUT handling is all about physics, especially that bloke called Newton re mass X momentum etc.
It doesn't matter whether its a motorcycle, sidecar or formula 1, the physics are all the same for cornering.
The biggy is polar inertia, imagine the bike as a long skinny weight and as it turns the heaviest end will want to maintain the existing inertia and direction while the lighter end will want to change direction quicker !
This really dictates the riding style trying to deal with this, setting up the bike or car or chair you can't have a neutral balance ie both ends the same as it becomes unpredictable so the norm is for the rider to select what they want under or over based on tyres, track etc
So my example from old days I built two identical cb 750 engines for two speedway chairs (sidecars)  Bear they were in Whyalla named  Peter Clark and Paul Hewitt . they had identical frames , Clarkies chair handled perfectly but Paul complains the motor was a dog. So I went to Whyalla for a meeting and spent some time with Paul at practice and his bike was sounding nice but understeering so bad it was driving hard into the wall on the exit and very very scary to watch, however the motor sounded good so putting Newtons hat I found a set of leathers that fitted me and decided to get on the chair for a session. The deal was instead of driving a straightish  line into the corner at the end of the straight he had to back off the throttle flick the bike sideways and instantly hold full throttle, he didn't get it right the first time and I aint lying when all I could see was the wall coming at me, so anyway second lap he got it right. After the session he said it was the first time the bike didn't understeer badly, I explained that steering slowly into the turn and his passenger jumping forward for the turn made for a very front heavy bike and that was what was making it understeer, not the engine.
The heavy front end resists a change of direction where the light end will.
So the bottom line for my point is even though they had and tried adjustable suspension on the chair it was all about the balance of the bike and the riding style that turned the bike from a pig to fun fast.
NOT MANY PEOPLE MESS WITH BIKE WEIGHT BALANCE, spend too much time on the norm adjustments like shocks etc I feel unless you do, your likely only going to be as fast as the next guy doing the same thing.
GRASSHOPPER SOHC HONDAS ARE THE MEANING OF LIFE.

Offline johno

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Re: Road racers rake and trail numbers, tree offsets, etc
« Reply #32 on: July 01, 2020, 04:32:44 pm »
Last post then Ill shut up,
Go buy a lead ingot , cut in halves, get bolts to hold onto frame somehow, get a set of scales, take a picnic hamper and chair to the track or a quiet section of winding road, weigh bike up front and back, start 55% bias to rear, try. then neutral & try then 55% front & try,   let the forum know what you think, ciao
GRASSHOPPER SOHC HONDAS ARE THE MEANING OF LIFE.

Offline johno

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Re: Road racers rake and trail numbers, tree offsets, etc
« Reply #33 on: July 03, 2020, 07:27:21 pm »
This are the lead ingots I use to clamp on somewhere
GRASSHOPPER SOHC HONDAS ARE THE MEANING OF LIFE.

Offline grcamna2

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Re: Road racers rake and trail numbers, tree offsets, etc
« Reply #34 on: July 03, 2020, 09:03:37 pm »
This are the lead ingots I use to clamp on somewhere

Get the riders to compensate and move around on the bike/pegs
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S',1982' Suz. GS450TXZ
  I love the small ones too !
Do your BEST...nobody can take that away from you.

 

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Honda