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faffi

A question about lean vs speed - again

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One of my current bikes is a 1999 Honda NT650V Deauville. I have put the rear preload on max, which raised the static ride height by 40 mm. Up front, I have raised the oil level by 5 mm to 115 mm from the top and raised the front 20 mm through extra preload. It handles like a bike much lighter than its 530 lbs wet weight would suggest - I will claim that it steers quicker with less effort than my MT07.

After raising it, the 150/70-17 Michelin PR4 will erase any trace of chicken strips before anything touches down. The 110/70-17 Michelin Pilot Street front has about 3 mm of chicken strips left, at which point the short peg feelers scrape hard enough to fold the pegs noticeably upwards. Still, by looking at the tires and also judging the sensation of lean, I would say that the bike heal over satisfactorily for a street bike.

However. Cornering speed is unusually low. As an example, today I went through a long sweeper with the peg feeler screeching while doing an indicated 55 mph. As a comparison, the MT07 will take the same corner at 70 with nothing touching down. Same with the GSX600F Katana I owned some years ago. In fact, I could do over 50 mph on my Intruder 1400, a bike not famous for its cornering abilities.  This repeats itself around just about any type of corner. And before I upped the preload, it would scrape doing 40 around a corner my CB400SF take at 65 mph with seemingly tons in reserve, although I had reached my personal limit.

Finally, the question; what in your opinion could be causing this bike to lean far and corner slow? 

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Let's recap:

  • Maxed out rear preload
  • increased rake angle (and trail)

The rider says:

  • Bike steers quickly (???)
  • Cornering clearance is sufficient
  • Low corner speed

Unknowns:

  • Are the tire sizes stock (it appears so)?
  • What caused the rider to desire to make this change? How did it handle before?
  • Resultant changes of geometry in wheelbase and swingarm angle
  • Other changes rider/owner made from stock that would affect the above?
  • Rider's application of standard throttle control (though presumed to be good and well handled)

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 Some of the questions I'd ask are what is the comparative overall weight of the bikes he is comparing against, where is the COG located on each of the bikes (higher? lower?) and how much can the rider hang off on each of them?

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I raised the rear of the Honda Deauville to gain cornering clearance, because it was scraping at ridiculous low speeds. I replaced the stock 120/70 front with a 110/70 because the former was worn out and I had a new of the latter laying around. Both are allowed for the 3.50in rim.

I do not know where the CoG is. The Deauville is a touring bike, weighing about 550 lb with a full tank. The MT07 is taller and much lighter at 400 lb wet. The GSX600F about 500 lb and the CB400 about 425 lb wet. They have a V-twin, Inline twin, inline four and inline four engine respectively, if that matters. 

But for me, the strange part is that the Deauville require a lot more lean for any given speed than anything else I have ridden. My latest bike, a Yamaha 650 V-Star Classic cruiser, is really low, yet demand a lot less lean than the Deauville. 

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Not that this will have much interest to anybody but me, but here is an update anyway 😄

When I bought the bike, it had a new Michelin PR4 on the rear and rather worn PR3 up front. Soon after, I replaced the brake discs and took the opportunity to fit a Pilot street, the mentioned narrower 110/70R17. When the new discs also warped, I fitted the spare wheel with stock, straight discs and a 65% worn Bridgestone BT30F mounted. 

With all these three front tires together with the PR4 rear, the bike demanded more lean than expected. With the PR3 and PS the bike steered fairly neutral and worked fine also on gravel. The BT30 did not take well to gravel. It also demanded a lot of counter-steering throughout every corner -- every time I relaxed fully the bars, the bike went for upright and a straight line. Unlike the Michelins - the narrow PS had no chicken strips in the end - the BT30 would fold on worn tarmac at peg scraping pace repeatedly, giving a sensation of falling over another 10 degrees (but probably no more than a couple). Each time, it regained grip slowly but smoothly, all I did was relax and wait.

You can see the slip marks, which of course went around the circumference on both sides, in this image

y4m8TQ15PTUvp2H6Jd1TvP7HjMdbnfUskFtBx2hm

The PR4, OTOH, had the most even wear across the thread that I have ever experienced - since I only ride on the road, up until now my tires have always been flat to varying degrees in the middle.

y4mzsOFF-MJKlna-TUbK8T-KGWMhZTC6mYmD5VLv

 

However, what I really wanted to discuss is the experience I had today on a new pair of tires. A lot of Deauville riders praise the PR2 as superb for the bike, so I decided to try that. Then I read a test of the Maxxis M6029 Supermaxx and went for that up front. Yes, I know many say never mix brands, and preferably not models. But I have done that since 1980, mostly with great results, but also a few that did not work. I have, though, had more tires from the same maker that did not work admirably. 

So how did the pairing work? Splendid! The only thing not quite perfect is that the bike now want to ever so slightly fall into corners and need a touch of input to straighten up - opposite to what it was, but also to a much, much lesser degree. Confidence and grip was excellent from the moment I left the garage with the fresh rubber, and there was no hint of insecurity or numbness throughout the 200+ mile ride. The rear tire lost any trace of virgin rubber within 10 miles.They even worked nice on gravel.

Most interesting, though, is that the bike now require much less lean for any given corner speed, acting similarly to any other motorcycle. How and why I cannot say, but I could corner faster than before but did not scrape once. Peculiar, but also very positive.

Maxxis fresh before the ride

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Ditto PR4

y4m92EqtYvlMmKOwAJ5ixlFEEaUdLj7hKpyha2c5

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Forgot to mention that I now also find myself going on the throttle noticeably earlier than on any other bike ever before, because early throttle application does not push the bike wide. Part is down to having little power, no doubt, but there is zero fighting or insecurity when opening the throttle once max lean is reached and the exit determined. I always felt the need to wait until I began picking the bike up before I began smooth acceleration to avoid running wide, but there is no need for that on this bike at the moment.

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Did you measure the difference in height of the front end when you changed the front tire?

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There was only 2 mm difference in diameter between the old Bridgestone and the new Maxxis front, so a 1mm difference in height.

I made a much bigger actual change earlier when I cut off just over 4 inches of the soft portion of my stock springs to stiffen the front end. This gave me about 15 mm less dive under the same kind of braking, meaning it should also hold the front end up a similar amount higher during brisk cornering. I also changed from 35 to 57 cSt fork oil, which naturally slowed down the rate of compression (and rebound) to compensate for the stiffer springs. Static sag was held the same, though, it is just the spring rate and damping that was altered. Steering felt more direct and connected, if that makes any sense, with the firmer front end. Yet the change in ride height did not change the need for additional lean, although I could lean a bit further before touching down. 

 

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So the bit about the old pairing needing active counter steering or it would stand itself up in a corner really strikes me as odd as it violates some core physics of 2 wheeled vehicles. I'm curious if something like the rear tire not quite being aligned or similar was causing that and swapping the tires corrected the problem indirectly. Just spit balling.

Glad you're having positive results after the change though!

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8 hours ago, faffi said:

There was only 2 mm difference in diameter between the old Bridgestone and the new Maxxis front, so a 1mm difference in height.

I made a much bigger actual change earlier when I cut off just over 4 inches of the soft portion of my stock springs to stiffen the front end. This gave me about 15 mm less dive under the same kind of braking, meaning it should also hold the front end up a similar amount higher during brisk cornering. I also changed from 35 to 57 cSt fork oil, which naturally slowed down the rate of compression (and rebound) to compensate for the stiffer springs. Static sag was held the same, though, it is just the spring rate and damping that was altered. Steering felt more direct and connected, if that makes any sense, with the firmer front end. Yet the change in ride height did not change the need for additional lean, although I could lean a bit further before touching down. 

 

The thing that made me ask about the height change was not the lean angle issue, it was that you said now the bike wants, ever so slightly, to fall into corners now, instead of showing more tendency to stand up. Sometimes a tire that drops the front down a little (even a small amount like that) can increase that tendency. And of course the profile of the tire affects that as well, and height and profile are certainly related so I don't know WHICH of those is the greater factor, in this case. 

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Ah, thank you for explaining. The tendency to stand up was very noticeable, I had to use quite a bit of constant force to keep the bike leaned over. Now, if I let go of the bars, the bike will take a little tighter line than the planned trajectory, but quite minutely so.  It was reasonably neutral with the Michelin fronts effort-wise, but with the soft front it was difficult to keep a smooth line around corners, the bike seemed to constantly vary lean and trajectory and the bike had to be constantly but gently guided. If that makes any sense.

Regarding profile; the Bridgestone had worn rather pointy, with little wear in the center, roughly inch wide, but with the majority of wear on both sides of center, making the tire shape somewhat triangulated until it again got rounded closer to the edges. The Michelins had much more even wear, I only have picture of the profile of the narrow one.

y4mXAlpQ7ipaU0tWQ1tH09PpF-mh4S7bhWWPBwPn

The Maxxis appear to have a quite large, flattish section on the center, as seen in my earlier post.

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