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sports tyre profile question

Discussion in 'Technical and Troubleshooting Torque' started by raven, Dec 29, 2008.

  1. I'm currently running the Pirelli CorsaIII on the rear with a rosso on the front - good combination btw, as I found the CIII front to be a little lacking in grip when pushed.

    I find generally, that the bike is harder than it should be to turn in and hold a line...I find I have to muscle it around a fair bit if I am really having a "go".

    Accepting that the suspension and geometry is pretty good, I'm fairly convinced that it is the profile of the rear tyre (190/50)...It has been suggested that going to a 190/55 on the rear will help the initial roll-in alot more and will help keep the bike on track mid-corner easier.

    Does anyone out there have a few thoughts on this, and why this might be the case?

    Ta. :)
  2. The Rosso's are interesting tyres in that the Rosso rear really does a lot to steer the bike through a corner. They're different to the rest of the Pirelli range IMO in how they do their thing, so my first suggestion would be that much of the difficulty you're experiencing is due to the mis-matched tyres. The Corsa III's are more rounded and a touch more stable as a result, but the rear won't be providing the steering effect to go with the Rosso front in the way in which they normally work.

    Pirelli do offer the Rosso rears in 190/55 too, and that would definitely be something worth trying if you want quick turn-in with lots of side grip due to the litre bike.
  3. Raven, my take on this:

    A 190/55 is a physically taller tyre. As the tyre is slightly taller, the profile of the tyre has to be sharper in order for the tyre to fit the same rim etc..This creates a more 'pointy' or triangular profile. So, as the tyre begins the lean, it tends to 'fall' onto its side quicker.

    Fat, low profile tyres tend to be slower steering. Narrower, higher profile tend to be quicker steering.

    [Edit] I couldn't find anyone who stocked the 190/55 in the Rosso. Seems the importer thinks that sports riders who want track day style tyres will have the III's and that Rosso owners don't want to go beyond a 190/50. As Flux points out, they ARE made, just when I got mine, the importer hadn't ordered any[/Edit]
  4. Thanks for the quick responses guys. :)

    I agree Stew...The CorsaIII to me, feels like it is trying to override the direction the front is taking (hard to explain - but basically it feels like the front wants to tip in and the rear won't allow it)...so I have to use more energy. This is something I had not considered when when I was originally searching for grip on the front-end.

    Thanks for the simple explanation Ceejay (I thought I had understood the priciple but was'nt too sure). I was figuring that the "taller" profile of the 55 should aid in the cornering being more willing to tip in etc.

    Ideally I want to try for a corsaIII 190/55, but if that's not around, I will give the super-corsa a try...Or a rosso 190/55, if i can get one..I will check.

    Seems I'm on the right track though, and that's what I needed to confirm. Thanks guys. :)

    John. (Oh...and merry Xmas) :)
  5. Pirelli Australia are an odd bunch. They market the Rosso over here as a sport-touring oriented tyre and the III's as hypersport road/track tyres.

    In the USA, Pirelli USA position the Rosso's as being more applicable across a wider range of bike sizes and conditions than the III's, and market them as gripper replacements for the OEM Pirelli Supercorsa Pro's (not including the special compound track-day varieties in that statement).

    In my experience with the Rosso's you'd want to be pushing stupid-hard on the public road to find their limits. A number of magazine tests have found them to be superior tyres on the track as well over tyres like the BT-016's, Michelin Power 2CT's, Dunlop Qualifier's, and so on. A different test ranks them about equal with the BT-016's around a track, but with both head and shoulders better than every other road/track going tyre on offer.

    It almost seems like Pirelli Australia is happier with the market thinking that the Corsa III's are "the Pirelli tyre to have", rather than pushing the Rosso's. Heck, even John above seems to be saying that the Rosso front is offering superior grip over the III's.

    Don't understand it myself (what Pirelli Australia are doing).
  6. Yep...the CorsaIII front is not that good of a tyre IMHO..Once it has a few thou k's on it, the grip is poor IMHO...Whereas the rear is BRILLAINT for grip/wear all the way to worn out. I have a nice even shape all the way across the tyre and that's a mix of commute and harder riding.
    I threw on the front rosso and found it better than the corsaIII front by a little bit, and it has NOT lost it's grip over time.

    I'm now sourcing a rosso /55 rear...or a corsaIII /55 if I have to.. :)

    I should mention that what makes the CorsaIII rar so good is the triple compound..as I was squaring off too much with straight compound tyres...If I end up with the Rosso, it'll be interesting to see how it wears overall. (although I lean towards grip primarily) :)
  7. The other thing about the 190/55 tyres is that they are obviously taller tyres, by around 19mm over a 190/50 tyre. This means that your rear sits higher by around 9.5mm, which generally reduces rake angle by around 0.4 degrees, which is quite significant, and it is primarily this which sharpens the steering geometry up and improves turn-in speed. It also shortens the trail a touch and makes the bike more unstable.

    You could get much the same effect by raising the rear ride height by 10mm with a 190/50 rear tyre.
  8. Also makes acceleration more sluggish and top speed higher.
  9. Bridgestones! :)
  10. You are of course taking the piss here, aren't you?
  11. think he's right. greater tyre diameter will do this. physics 101
  12. My 'quest' is for a tyre shape that will allow the bike to hold it's lean angle.
    I do understand what you are saying though Stew.

    I have found that the 50's are just not so willing to roll onto their side, and when they do, seem to have a desire to want to stand up unless I use alot of body language to keep it down...I am after a shape that will alow me angle the bike over and use less energy in actually keeping it there. Of course...the geometry change will increase the agility of the bike to, which in the case is just a by-product I'll live with in order to get the other. :)
    At least...that's what I'm trying to do...even if it turns out to be wrong.
    I was actually planning to drop the rear-end a bit in order to balance it all out. (agility vs line holding)

    I rode a blade with a 195/60 (?) slick for a half hr or so on the reefton. I could not believe how well the bike tracked a line...felt more like a 600rr in the way it would tip in and just stay there, as compared to my bike wanting to fight me to try and remain off the angle on the lean in. It's has thouroughly pissed me off...no wonder I can't hold a line so easily...
    Yeah...I know...slicks are a different kettle of fish, but I'm hoping to get closer to that "feel" through corners, if ya get my drift, mate.

    Keeping the thou 'over and down' is requiring too much work...

    Or maybe I just don't understand it al enough and might be barking up the wrong tree...that's why I value the advice and the chance to discuss it a bit. :)

  13. I know that. The question was about 'sluggish'. The difference in tyre height and therefore circumference is minimal and the net effect on any bike, let alone a machine with in excess of 150rwhp is negligible. The 'higher' top speed might be attainable given perfect conditions, but we'd be talking about the difference of a few k's. As for acceleration, have a good dump in the morning and you'll see the same.
  14. Technicall, that is probably correct - makes sense...but with 150hp+ at the rear wheel, I'll live with the little less blast of the mark. Not worried about top speed too much...since I won't be getting there too often..except the track.

  15. I know the difference in the acceleration and top speed are minor, but they exist as much as this difference here. So, if we're gonna get pedantic about "how much" effect it has, then the ride height is actually only increased by 5mm, not 9.5mm, as the 5mm extra on the top of the tyre has no impact on ride height......
    Where did you get 19mm from FLUX?
    Also the effect of the reduced trail is about as significant as the effect on acceleration.....

    It's the combination of all these minor differences that make it a different feeling/performing tyre. If there was no noticable difference why would they make the tyre in the first place? Why would manufacturers recommend the 55 profile over the 50 on some bikes?
  16. True, but we're talking about some people who will spend hundreds of dollars on PCIII's to gain 2-4hp in some cases(~2% gain) so a 1% difference in top speed or acceleration should in theory be significant enough to warrant a mention I would think.
  17. well crap!...getting a 190/55 in a Rosso or even a CorsaIII is proving to be very hard!...I've rang most of the regular joints, and of course...no one has one (That's because "I" want one of course)

    Plenty of SuperCorsa's in the /55's but a little on the soft side for my needs right now.

    Anyone know of a Tyre joint that might have one?...One of those little specialist shops perhaps?...or some big tyre place that I don't know of, that's outside the usual list...(thinking to self)

  18. You're describing 'me'...I fitted a PCIII...although I gained 10+hp with a pipe as well...and of course...it was'nt only about HP... :p
  19. I have found that by going to a taller profile tyre, it will tip in slightly easier, but then requires more effort again to get past a certain lean angle. True it will hold a constant lean/line, but mid corner adjustments become more difficult. Good for a track/constant radius corners, not so good for the road.
  20. John, I don't have what you want in stock at this very moment, but I can certainly order it in for you, might be mid next week though, because most distrubutors are closed til the 5th of Jan.