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Old January 5th, 2013, 12:16 AM   #1
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Truth about tyres and traction control

Ok, so this moring I was posting some comments on the back to back suspension comparo and a question was raised about DTC and tyres..

So to assist with the question I ran a Dunlop and a Pirelli today... But first I will try to give some technical information before i share the results.

We will deal with the edge of the tyre because that is where the DCT is mainly in operation, the Dunlop is 24mm less in total diameter, this equates to approximately 1.5 pulses less than the Pirelli SC fitted as standard.

Ducati have programmed the DCT to measure pulses on the front and rear using a 200 series Pirelli so in simple terms any 195 series tyre fitted will need to wheel spin a fraction more before the differential between the front and rear is triggered and the CPU engages traction control.

What does this mean?

Well, the compound is of no interest to any of us, means nothing and will not effect the DCT, it will mean u will have more grip before the bike wheel spins if u fit a softer compound tyre. And visa versa if u fit a hard compound.

However, a smaller tyre will effectively mean u will have a very small increase in the amount of wheel spin in each setting. Unless ur name is Casey Stoner or Cal Crutchlow or my favourite Troy Baylis u will not truly notice much of a difference.


Today I ran a stock SC 200 series rear and a Dunlop N-tech 195 medium compound slick. Made no changes to the rear shock after setting it up on the Pirelli.

The Pirelli was loose after 5 laps with the DTC set on 2 I could be ham fisted and get the bike sliding but totally controllable with the DCT only coming in if I was on the edge of the tyre knee on the deck past the apex and driving hard off the corner.

The Dunlop felt like it was getting better drive which u would expect from an N-tech, however the traction control was slower to react which actually made sliding the rear more progressive.

I did try switching traction control levels, this was interesting, effectively it felt like the Dunlop had made the DCT switch a level, so the Dunlop felt like it was on setting 1 with more wheel spin, yet the DCT was on setting 2.

The final point here is that a 195 will wheel spin a little more so the answer if you as a rider are worried about this is to run the DCT back one level. So 3 instead of 2 and so on...

Just for those of you who have followed my suspension changes, the Penske was great today and once I've got the ohlins I will have 2 of these units available for anyone with a standard who is keen to change out the rear shock... They will be set up for fast track work, for a rider and gear weight of 96kg. First in best dressed... See attached photo for a look...


I hope the above info is of assistance to those of u wondering how much truth in the tyre and DCT debate...

My answer is fit the rubber you like, set your traction control to the appropriate level and ride the bike ...


Have fun

Bowdy
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Old January 5th, 2013, 02:14 AM   #2
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Hi Bowdy,

First, thanks for your postings - they are great

Did you only change the rear ?

I was on Brno Late sep just after I got the Pani - I fitted it with my favorite tire - Dunlops KR 106 120/70 and KR 108 195/65 on OEM wheels.

The DTC was very active and I ran it in level 1.

I just went to my garage to check the diameter on the tires (not fitted to wheels) - measured on the edge on them. Result is:
Front: Dunlop 505 mm and Pirelli OEM 120/70 is 497 mm
Rear: Dunlop 519 mm and Pirelli OEM 200/55 is 526 mm

So - when riding in corners - on a Pani fitted with Dunlops - the DTC will get a few more pulses from the rear(it rotates faster due to the smaller diameter) and a few less pulses from the front(due to the larger diameter)
The DTC will then think, that the rear is spinning and thus start to regulate the power.

The low pressure on Dunlop rear(23 psi) could give us an even lower rolling diameter.

This measurement on the tires explains to me why I felt that the DTC was a bit to active - even though I havn't tried the Pani on OEM tires.

DTC level 1 with dunlops works ok, but I would love is someone could adjust the DTC a bit just to adapt to the different rolling diameter on the Dunlops.

I know, that slipmaps in DTC systems is quite complicated to adapt to tyre behavior under accelerations - and not just the rolling diameter. For my level (National chanpionship and Nordic BOTT) an adjustment for the difference in rolling diameter will be fine.
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Old January 5th, 2013, 02:36 AM   #3
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Fascinating to read, but makes me realise how little of this bikes potential I can actually touch
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Old January 5th, 2013, 02:42 AM   #4
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Yep, I wish I were even close to level of ability! Exc. information!

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Fascinating to read, but makes me realise how little of this bikes potential I can actually touch
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Old January 5th, 2013, 02:58 AM   #5
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Yep, complicated, measure the tyre inflated on a rim it's important to consider tyre radius also, the 200 profile is a steeper profile.

Ducati do actually provide some pro-stock and semi factory riders with an updated DCT for the dunlops.

I will take a look at the front tomorrow at the track and measure the edge of the front to compare, if the front is different then the challenge becomes more complicated.

Slicks create a challenge because the front and rear profiles and tyre radius is different from make to make. However road tyres (front) are 120-70-17 across all manufactures which gives the CPU it's base line.... So the basis of the complicity for the pulse count is dependent on the front tyre which the base line.

Remembering that the DCT takes the signal from the front and compares it to the rear.. I'd like to dig a little deeper in to the issue with slicks.

I totally agree with you regarding pressure too, Side wall flex on slicks also creates a third dimension, however the tyre flexes it still needs to roll its full diameter.

At the moment I believe it's integral to the front tyre, I will test this tomorrow by running a different size front and not a 120-70.

It's going to be an interesting thread.

Cheers
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Old January 5th, 2013, 03:10 AM   #6
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By the way, measure the diameter, 200 series Pirelli is 1646mm
The Dunlop is 1624mm which means the tyre travels 22mm less per 1 full rotation which equates to a difference of 1.5 pulses on the rear, at over 200kms a fairly large difference.

I will take the time to calculate the difference at a number of different speeds to give us all a better view of the impact of a smaller diameter.

For the road I believe this not to be a problem.

Should be interesting tomorrow
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Old January 5th, 2013, 03:14 AM   #7
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Hmmmm got to think harder too, less is more... Will sleep on this one, between us we could find a setting...

I will actually see if I can get some details on the Dunlop setting for you.

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Old January 5th, 2013, 05:46 AM   #8
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Thanks for the write up Bowdy. So I guess for all those switching to the 190 Pilots or the Q2s will be looking to move their DTC up from 1-2 to maybe 3-4 depending on their riding preferences/experiences. I only mention this because it seems to be the most common tire size change within this forum. Bottom line is to test the bike out, after all there are 8 levels of DTC.
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Old January 5th, 2013, 06:55 AM   #9
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Hi Bowdy,

You are going to the track tomorrow - where I again just can sit tight and wait for the spring to arrive

The numbers you post for diameter - I suppose that you mean circumference of the tire.

Any info regarding use of the Dunlops are very much appreciated.

Even though I think it is a long shoot - I will try to contact my dealer on Monday - and see if he can source some info from Ducati regarding super stock maps.
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Old January 5th, 2013, 10:53 AM   #10
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Sorry for the confusion in terms, yes I mean the total circumference at the edge, I will also chase to see if I can get more detail on the dunllop map...

Gman, I have not measured a 190-55 tyre but will do so, in real terms the traction control is adjustable and fitting a smaller tyre on the rear should not cause a major issue if the front is the right profile and size.

I do believe there are small variances depending on manufacture, I.E Michelin front tyres have a more rounded profile on their 120 section front than say a Bridgestone. The difference is even more obvious with slicks, which is why some make the bike steer quicker and some offer better lateral grip.

Eventually it comes down to preference, I like Michelin road tyres, have them on my road bikes, love Dunlop N-tech slicks...

The thing for everyone to remember is a 190 will flatten out on the rim more than a 200 section. It's why WSBK went to 16 inch rims that were 6.25 wide, to allow a 200 section tyre to sit on the rim with the same cross sectional profile as a 190.

This years change to 17" rims in WSBK will be great for those using pirelli rubber.

I'm still looking at the distance traveled at speed to clarify the difference then we can clarify the change in levels for tyre size...


Hope that all makes sense.

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Old January 5th, 2013, 11:52 AM   #11
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Quote:
Originally Posted by gman74 View Post
Thanks for the write up Bowdy. So I guess for all those switching to the 190 Pilots or the Q2s will be looking to move their DTC up from 1-2 to maybe 3-4 depending on their riding preferences/experiences. I only mention this because it seems to be the most common tire size change within this forum. Bottom line is to test the bike out, after all there are 8 levels of DTC.
Actually you'll need to go the other way with the TC if you move to a 190/55 rear. The smaller diameter rear will be rotating at a higher RPM relative to the front (more pulses from the rear sensor ring at a given ground speed). I have Bridgestone S20's on mine presently (for road use), and found that even though the brand-new rear Bridgestone 190/55 was 5mm larger in center diameter than the worn stock Pirelli 200/55, the TC was noticeably more active accelerating off corners at the same setting. That was likely due to the ratio of rear-to-front edge diameter being smaller than the stock tires. Didn't measure the edges new, but should have; we're not really worried about TC when the bike's stood up, after all. Depends on the actual tire dimensions of the brand you choose, but I'd say going one setting lower (2 vs 3 for instance) gives fairly comparable TC intervention when going to a 190/55 vs the std 200/55.

Heck; you can calibrate cheap push-bike computers by inputting actual tire dimensions into them, so hopefully someone will figure out how to hack that function into the DTC via dash settings one of these days without having to resort to high-cost aftermarket systems like Nemesis. Seems a shame to chuck working TC just because it has one set of tire dimensions hard-coded into it. And about 4-5 levels that are too intrusive to be of use...

Last edited by Steve B; January 5th, 2013 at 12:06 PM.
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Old January 5th, 2013, 04:51 PM   #12
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Yep that's what I meant when I said less is more, I'm on to it, and ur correct about smaller and more... Changed the front this morning, holly crap... Running a different front really screws with it...

I am going to see if I can hack the system, keep u all posted...
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Old January 5th, 2013, 05:17 PM   #13
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I've got to believe Ducati has got some way of altering it for racers that run in spec tire series. Have you tried contacting Ducati racing support ? racing.support@ducati.com
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Old January 5th, 2013, 06:20 PM   #14
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My understanding may be wrong, but I thouht that the brief roll before the DTC light goes out was the bike calibrating the front and rear tire diameters, part of the boot-up sequence.
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Old January 5th, 2013, 06:23 PM   #15
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I think thats the ABS sensor calibration sequence you are talking about.
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Old January 5th, 2013, 06:55 PM   #16
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Quote:
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My understanding may be wrong, but I thouht that the brief roll before the DTC light goes out was the bike calibrating the front and rear tire diameters, part of the boot-up sequence.
Nah, thats just the DTC waiting for an input from each wheel sensor to validate that the sensors are working. My Aprilia does the same thing at startup. The Aprilia however, does include a calibration function to account for different tire diameters AND gearing changes. I'm at a loss why Ducati doesn't include the calibration feature.
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Old January 5th, 2013, 10:18 PM   #17
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Ok, first of all I'd like to say thanks to Gman for imitating the question and to those of you who have added valuable input to the thread.

First some background, for the first 8 years as a professional engineer I worked as a systems and interface engineer on CNC and robotic equipment in automotive.

Robotic equipment uses an impulse encoder to send a measured input to the CPU to translate mechanical movement in to digital input. This is then translated in to measured movement from a set point to points of reference in the programming.

The subject we are all trying to solve has finally shaken off the dust from the old grey matter and through out the day I've measured tyres and tried a number of configurations...

Some machine shops will make the same component in different sizes, the easiest way to do this is called parametric programming. Instead of writing a separate program they tell the encoder to count the pulses in different ways, I.E a measurement of 1mm might be 2 pulses for a large part and 8 pulses for the same shape but smaller.

(Sorry if I'm going on)

However old machines did not have the programming or capability to construct the algorithms in the memory. Wen this was the case the simple solution was to change the encoder so the count was different.

We in effect are doing the same when we change the size of a tyre. This was my light bulb moment today... If we are changing the mechanical count by reducing the tyre size then the obvious and simple solution will be to calculate the change in pulse rate between a 200 section tyre and a 190 section tyre and manufacture a new disk that brings the pulse rate back in to line with the programming.

A very simple solution that is easy to manufacture and fit... This gents will be my next step. It will not effect the abs because the abs works on the principle that when it stops seeing a pulse it activates.

I am truly grateful for all input over the last day or so, this solution if effective will be great for those who race and use different sizes depending on rain, slick or make of tyre..

Your thoughts gents
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Old January 6th, 2013, 02:35 AM   #18
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Clever thinking and a viable solution, but not sure you will get the fine granularity needed. Adding one or two pulses may not correlate to what you need. If I get a chance tomorrow (back at work) I will throw some number at a spreadsheet!
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Old January 6th, 2013, 02:52 AM   #19
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Thanks Pete, the interesting thing with this will be getting that balance, let me know if its worth exchanging email addresses re this subject.

Still haven't measured the 190, will do this tomorrow and give u the difference between the 200 section and 190 section and post the numbers, the 195 Dunlop is approximately 24 mm less in circumference. It's taxing the ol noggin...

Chasing info on how to access the DCT

Back to work eh.... Bummer
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Old January 6th, 2013, 05:54 AM   #20
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Originally Posted by Bowdy69 View Post
Thanks Pete, the interesting thing with this will be getting that balance, let me know if its worth exchanging email addresses re this subject.

Still haven't measured the 190, will do this tomorrow and give u the difference between the 200 section and 190 section and post the numbers, the 195 Dunlop is approximately 24 mm less in circumference. It's taxing the ol noggin...

Chasing info on how to access the DCT

Back to work eh.... Bummer
How much did it affect the gearing with a 24mm circumference difference? Where did you get the Penske? They just released the 1199 spec recently?
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