Effect of wider rear wheel

[dandywarhol]

But that could all change if you modify the ride height by fitting a longer shock or diferent dogbones - it's the relationship between the pivot points of the axle, swingarm pivot and the gearbox output shaft that matters. If the gearbox shaft centreline is above the axle/swingarm pivot then the rear will squat, if below then it'll rise.

[Beau]

agreed... but then you've made a massive change in geometry to achieve it when you could have achieved the same thing with a suspension change and maintained the bikes geometry the way the manufacturer intended it to be.

I'll have to reserve judgement until I ride one with the other mods... who knows, I may become a convert!

[Kayla]

agreed... but then you've made a massive change in geometry to achieve it when you could have achieved the same thing with a suspension change and maintained the bikes geometry the way the manufacturer intended it to be.

I'll have to reserve judgement until I ride one with the other mods... who knows, I may become a convert!

But, and here's the thing, the TRX's geometry as standard is a bit wishy washy for some (as is the seating position, it's neither nowt nor something). I found, maybe because of misadjusted or worn out suspension or whatever, that the front tended to run wide and the bike felt like a bit of a barge. I know it's all personal and subjective and opinions are like bums- everyone's got one- but I found that my bike behaves in a more predictable manner with the geometry set a little sharper, but I'm used to riding smaller capacity sportsbikes and I suppose getting the TRX closer to that made me feel more comfortable on the bike.

[Beau]

Exactly... it all depends what you're used to.

[NZTRX]

Um, Ive got a YZF750 Swinger on mine with the Orig. wheel running a 170 Conti Road Attack and its Fantastiche!!! wouldnt have it any other way, turn-in is still just as quick (as 160 orig.) and the bike feels like it has more confidence on the high lean angle. My chicken strips are only 2mm wide so i reckon thats the way to go!!
Conti reckon theyre safe up to 50.9 degrees lean angle so i reckon im getn at least 48 degrees on my 170 rear.

only problem i found was i had to machine the YZF750 axle down so as to fit the Orig TRX wheel bearings and wheel, ooh and a new thread for the TRX Bolt.

I wish my Home Detention would finish so i can enjoy Trixy, havnt ridden her fo 6 months dagnabbit!!!

[sandmacker]

Have you changed the width of the front tire ? . I've heard also folks downsizing their rear tires ontheir 1000 super bikes to get more 'flickability' into their bikes . I know this is an expensive option , but look at some BST rims . They will transform your bike from all accounts . Not that I'm an expert , but a wider front tire and a steeper rake angle would allow you to brake harder and further into the corner , and then use the trixies quick handling to drop and squirt the power on early as poss . I personally think 180's or 190's are overkill considering the power the TRX has . I personally think you need extra traction into and through the corner ,not out of it , and I believe it would be gained by fitting a fatter front tire ,and going for a 160/170 rear . If anything , I find the front end on my TRX a bit unsure when I lean it right over , but I also have shit tires on ATM . BTW , some people have reported up to 3 seconds a lap improvement weth BST rims , and it's been said by some to be the biggest improvement to your bikes overall performance. But you probably already know this ,, right ?

[sageracer4]

can i ask what change to lap times these modifications and settings have had? there is a lot of discussion on settings,parts etc but what have been the gains,in lap times, of these over a standard swingarm/wheel combo? Just wondering if the amount of change is more for aesthetics than for performance gain?

[dandywarhol]

All in the heid IMO

[Tarwetijger]

Ah, nice to see that my topic still is interesting to some of you.

The frontend was and still is a YZF750 USPD fork with Marvic rim. The tire size remained the same (120/70/17).
For trackday season 2010 I put back in the original swingarm and rim with a normal 160 tire.
Compared with a trackday at Assen in 2009 (when I was riding with a 190 tire), my best laptime dropped 3 seconds in 2010, riding a 160 tire. However, you have to take in account that my track riding skills should have been improved in the mean time.
On another track the difference was even greater, but the old laptime was longer ago (about two or three years).
On the pictures (made by a professional photographer) it was really obvious that I had a lot more ground clearance. In some corners it was even harder to get my knee down.
So, in a nutshell, I'm so convinced that Mr. Cocco is right, I already sold the Marvic rear rim!
I'm not sure what to do with the YZF swingarm and rim, because there's still a perfect Pilot Road 2 tire fitted on.

[dandywarhol]

Yamaha spend millions of yen on research and development and come up with a reasonable compromise to put on the market - bearing in mind, the TRX was designed in the early 90s.

They might come up with no more than average suspension components (although they own Ohlins ) but it's done to a cost. What they usually get right is the configuration of frame geometry, wheel width and tyre sizes (although I grant you the 60 profile front is not to everyone's liking).

So most mods to swingarm/wheelwidth/tyre size etc. is really to give the owner's mind a treat IMO - I've nothing against customising a bike to individual taste but just remember the time and effort put in by the manufacturer at the design stage - it usually works well enough as a package.

[NWS870R]

The TRX was a parts bin special (leftover parts from many other models) which Yamaha put out while they concentrated on the task of developing the R1 & R6 models - it just so happened that the concept actually worked in the real world. Had they spent more on development & priced the bike realistically they may have also had a commercial success. They didn't & it sold in meager numbers which is why they are becoming in short supply now that people are remembering that they were actually pretty damn good.

Whilst manufacturers may spend millions of yen on R&D they quite simply don't always get it right & some models end up ripe for modification - the Rex is a pretty good example of this (although the starting point ain't terrible)

[sandmacker]

I get the impression that Yamaha built the TRX with the idea that people and racers will hang different units off their bike.
They have a 6sp racing gearbox on the market , so they designed the bike for the track if desired . As we know the frame and the motor are sweet , and in their own way , allowed the rider to choose what suspension , tires and wotnot they wanted to make it handle. If I'm right , they won the battle of the twins in 96. I'm not making claim that this is correct , but it's the 6sp race gearbox that has me leaning this way along with the fact that they hung shit brakes off it and some front forks that could of been a little more up market (R6) ,that would of been a little more in line with the character of the bike. Again , we're aware they aimed it at the duke SS with the intention of making it more user friendly and if so desired , to give them a fright on the track . Unless we're a serious racer ,as some of you fellas are , the most of us will get by with a few tweaks here and there , a set of cans . Tuning a bike to make it handle the way you want is a very personal thing , of which most of us ,including me , no little of . It's a trial and error thing and just when you think you've got it right , something else will conjour up on ways to make the bike do it better . Now I'm off to drop my front end another 5mm to quicken the steering , and see how it feels in the hills LOL