Spec'ing a single tire

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John Kwong
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Spec'ing a single tire

Post by John Kwong »

Hi All,

There has been some discussion so far this winter amongst the Prairie Clubs and Shops about unifying the tire rules for the Senior Briggs classes. Some clubs are running the MOJO D1 mandated by ASN National rules while CKRC has had an open tire rule for a long time and EDKRA recently went to the MOJO D2. The CKRC has led the way with large Briggs grids and most racers are on the MOJO D2 tire. EDKRA joined us last year in using the D2 and now Regina is showing interest by also wanting to utilize the D2 tire. There have been several benefits to using the D2 over any other tire:

1. great handling
2. consistent tire wear and usability through its life span
3. easily obtained
4. much wider tuning window than the harder and narrower MOJO D1
5. 2nd hand tires from Rotax are free or nearly free

The West Coast Kart Club at Greg Moore Raceway has decided to go from MG Reds to Vega Blue 6" tires for next year. Even though their Briggs numbers have come up significantly in the past year, the likelihood of any of them travelling to Alberta or Saskatchewan is unlikely. Currently, the CKRC has an Open Tire rule for Briggs Senior and Masters but most racers just used the MOJO D2 for the reasons above. So I feel it is in our best interest to perhaps limit the tire we are going to use, to the tire most people are already using locally. This is so that we can align the rules in our region and hopefully motivate more travelling by racers. Most Briggs racers will only go through 1 or 2 sets of tires in a whole season. By eliminating the purchase of a different set of tires for a single race this will lower the cost for people to come to our races.

Let me know your thoughts on this.

John K
Last edited by John Kwong on Sat Dec 19, 2015 12:46 pm, edited 1 time in total.
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phil
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Re: Spacing a single tire

Post by phil »

I would suggest leaving it to either Mojo D1's or D2's, and either the 6" or 7" rears, which will mean most, if not all will be on D2's, but would not exclude Jr's moving up, or people from other clubs.

Phil

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Re: Spacing a single tire

Post by Mark »

I think what we have been doing is what makes most sense for all concerned. The shops will also be more efficient if they have fewer sizes/kinds of tires they need to stock.

Aligning the rules between neighboring clubs can only serve to improve inter-club travel and participation.
Mark Hillier #44 VLR Senior, Shifter

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John Kwong
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Re: Spec'ing a single tire

Post by John Kwong »

Phil,

Okay. Lots of ideas in that statement. Not sure what you mean.

For clarification:

D1 = 6" rear tire. 7.1 in this compound is not available anymore
D2 = 7" rear tire. Not available in 6"

They didn't even run the D1 for Senior Briggs at the Canadian Nationals. The 6" Vega Blue was used.

I agree most people in Senior Briggs will probably be on D2's which is where the prairie clubs are leaning so that people from other clubs can travel without an extra tire expense to do so.

CKRC and EDKRA who have the largest numbers of Briggs racers have pretty much unofficially adopted the Mojo D2 as the spec tire and Regina was just wanting this more formalized so that they could convince their racers to follow this tire rule too. Rules parity in a region will grow participation in the long run and the Briggs classes have this for the most part except for the tire rules we use and overall max width which ASN is apparently looking at for this coming year.

John K
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phil
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Re: Spec'ing a single tire

Post by phil »

Jr Rotax has been running 7.1" D1s since 2012, and I have been using some of them on TAK karts. Longer life, and available in the tire bags, not sure how they would fare for lap times. Jr2 four stroke runs 6" D1's, and would have to buy rims when they move to Sr. They will likely end up doing that to be competitive, but I don't know that it should be forced. I just think closing it down to Mojos that are readily available makes sense, and not just "open". Wets could be regulated to Mojo as well.

Phil

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Re: Spec'ing a single tire

Post by John Kwong »

Ahh. I didn't know they still made a 7.1 D1.

Mojo seems to be the natural choice as far as brand is concerned, so I don't think there will be any push back on that. Leaving the racers with a choice of what compound to run and tire size could be done but I am not sure what that would accomplish other than leaving an expensive testing option available.

As we have found so far, the Mojo D2 4.5/7.1 combo has been a very good tire for Briggs in Alberta and my guess is that is what will continue to be the most popular.
As far as rims: Colin Peterson used to run the 7.1 tire on the narrower rims and was fast with those. It just changed his gearing because the tire was taller.

Rain tires being only Mojo is probably the most logical solution. There is a huge positive difference in performance by other brands of wet tires The Vega wet tires for instance (Ask Dave Henning).

John K
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Rob Kozakowski
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Re: Spec'ing a single tire

Post by Rob Kozakowski »

Just to clarify, for our club races in Briggs Senior/Masters, EDKRA has offered the option of:

7.1 D2 (everyone is using it because it is fastest - and there's lots of good used ones for free behind the race trailer)

7.1 D1 (it's an option that nobody uses - there's some decent used ones for free behind the race trailer, but they're not as fast)

6.0 D1 (it's an option that nobody uses - the used ones are normally complete junk by the time the junior racers replace them... and they're slower)

Bottom line, we do provide an option - but the "right" choice is a no-brainer, which has essentially made it a spec D2 class.

Since everyone in the province uses them, and they are readily available (at no or nominal cost), it only made sense to spec the D2 for the Summer Challenge, rather than making people worry which tire to use.

I think we require Mojo wets.

For the sake of the dealers, it's certainly easiest to keep it Mojo, so they don't have to stock additional tires for a single class.

As for rims, I know that Scott Campbell ran the 7.1 D2 on the narrower 180mm rims at the Summer Challenge... I think they worked ok for him ;)

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Re: Spec'ing a single tire

Post by Tony »

What has not been mentioned so far is a timeline to use up old tires (non Mojo brand tires).

The only practical reason for not specifying the Mojo brand as the spec tire is that they do not produce the softer Prime compound for the 6" wide rim which is the maximum size generally allowed to run in the East and at the ASN Nationals according to the ASN Technical Regulations/ Those same regulations specify a minimum rear width of 50" not the 55" that we allow to accommodate the 7' rims.

While there is little doubt that the Prime Mojo D2 compound on the 7 inch tire is faster than the D1 that is the only available compound on the 6 inch tire it is not clear that the 7" tire itself is inherently faster than the 6" tire when run at the same rear width.

It would perhaps be more reasonable to require any newly spec'ed Mojo tire to be used at the Alberta Shootout events, while allowing people to use any brand of 6" wide tire at CKRC club events for the 2016 season.

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Re: Spec'ing a single tire

Post by Tony »

Couple of more points to think about with regard to spec'ing a tire.

The Mojo D2 worked very well at Varsity but apears to have some issues at the Strathmore Track.
It is fairly consistently reported that a new tire takes 50 or more laps to come in and that it is significantly slower per lap than the old tires before that ( 1 or more seconds per lap).

We should be picking a tire compound that is fast out of the box and then gives consistent lap times thereafter for a lot of laps. A tire that requires this amount of running in adds to peoples costs in requiring multiple trips to the track before they are fast and may also upset the setup of the kart as people fight to find the lost speed with unnecessary adjustments. ( this running time while the tires are slow may just cause wear and tear on equipment rather than be valuable practice time)

6 inch tires are often cheaper than their 7 inch counter parts - we should not be forced to pay more for what might well be a slower tire.

When an organization specifies a tire for a certain class hey should be getting a payback from the tire manufacturer for this captive market (te manufacturer obviously has lower promotional costs). Currently any refunds from the Heidenau who make the Mojo tire are likely directed to the Rotax Karting program and are certainly not slated to go to the Calgary club. If we are to specify a tire we should maybe do our homework first and plan for such a tire in the 2017 season

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Re: Spec'ing a single tire

Post by John Kwong »

This is my experience with tires in 2015. For the first half of the season on our new asphalt, new tires were slower than scrubbed in tires. Only my Rotax kart ever saw new mojo d2's. The strategy went from putting the new tires on for qualifying to putting them on for the practice session in the morning. This seemed enough wear to get them to work on our virgin asphalt. My tires on the Briggs and Rotax kart were smooth after all sessions in the first half of the season. It was not until the second half of the season that we saw normal graining of the tire surface as the oil and sand had been worked off of the racing line of the track. We also were running extremely high tire pressures around 20 lbs in order to get any heat into the rubber. Now that the track surface has been worked in, I believe the phenomenon we experienced with new rubber being slower is now behind us.

Even though we have been running officially as open tire for Briggs, the D2 continues to be the tire of choice for the many reasons I stated above.

With the weak dollar, I doubt you would be able to buy any competitive 6" tires for the same or less than the mojo D2's. Along with the local availability vs shipping in sets of another brand of tire will make this uneconomical.
West Coast kart club is going to use 6" Vega Blue tires in 2016 after using the harder 6" MG Reds in 2015. These two other brands are your two other brand choices along with Bridgestone or Dunlop but no one really uses those in Canada anymore so availability would be expensive.

Payback from tire manufacturer
There was only one tire manufacturer (Burris) that I can remember ever offering a club discount for using their tire exclusively. CKRC never pursued this as the tire sucked. Unfortunately, unless the local importer is willing to give the club some sort of payback, the market is just to small to be on the manufacturers radar.
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