Why is wheelbase important

Wheelbase is a factor of: seating position, fuel tank, engine and gearbox length

A huge amount of fan attention has been focussed on wheelbase this year.  Even in recent years some teams’ preference for longer wheelbases has driven a lot of assumptions.  A typical F1 car is over three metres long; this length is largely dictated by the need to package the driver, fuel tank, engine and gearbox along the centreline of the car.  With engines being fairly fixed in length, fuel tanks needing to be sight centrally for weight distribution reasons, it settles down to fuel tank length, gearbox length and how far back from the front axle line the driver sits to determine the wheelbase.

Wheelbase length is often seen primarily as a factor in how the car suits fast or slow turns.  The common assumption that shorter cars go better around slow tight bends and longer cars go best in longer fast turns.  This proves to be largely false, the difference in the longest to shortest cars is only a few percent, certainly not enough to substantially change the cars ability to corner around the hairpin at Monaco.  Indeed Monaco proves to be no litmus test for wheelbases as longer cars have frequently won there.  I am told that wheelbase changes by a few percent, affect lap times in just thousandths of a second.

If wheelbase is not a factor in agility, then why is it so important and closely guarded? There’s two main reasons: weight distribution and aerodynamics.  As the components that decide the wheelbase are also the major masses in the car (driver ~65kg, engine 100Kg, gearbox ~40kg) by placing these strategically along the wheelbase a more forward or rearward weight bias can be achieved.  This is critical as it decides how well the tyres are worked.  Tyre are the biggest area for potential lap time improvement, even more so than aero, however far harder to achieve.  Teams have run up to 49% weight over the front axle in 2009, the cars layout will have a major impact on how much weight gets placed in the right place, without too much ballast being needed to meet the desired distribution.  For a more forwards weight bias you want the major masses moved forward, thus the drivers feet closer (but not allowed in front of) the front axle, longer gearboxes to space the heavy engine and gearbox from the rear axle.  In moving these masses sometimes wheelbases have to be altered to get the components in the right place.

Then there’s aerodynamics, probably more important than layout as tenths gained from aero are easier to reap than with tyre usage. Teams will want to create space for the airflow to twist and turn in order to get the downforce figures the designers are chasing. Often this has lead to long wheelbases as the designers want space between the front wheels and sidepods for bigger bargeboards, or space between the engine and rear wheels for a slimmer coke bottle shape. Ferrari has probably been the team happiest to stretch wheelbase for aerodynamic benefit. This year BMW Saubers Willi Rampf told me the cars wheelbase was purely a function of the cars aerodynamics.

But, if long wheelbase is an aero benefit and has no loss in agility, then why doesn’t everyone go for longer wheelbases. Well, the offset of along car is weight. By definition a longer car has more structure and hence will be heavier to achieve the same stiffness as a shorter car. Teams with restricted resources may not be able to afford the resources to design ever lighter structures from more expensive materials, this perhaps backs up the reason Ferrari go for longer wheelbases, they can afford the expensive carbon gearboxes and months of detail design work to make a longer car as light and stiff as a shorter one.

15 thoughts on “Why is wheelbase important

  1. I have a question regarding the Ferrari wheel covers http://www.terra.es/addon/img/deportes/13182faseara2p.jpg.

    Article 11.4 of Technical regulations says that:
    – no part of the car, other than those specifically defined in Articles 12.8.1 and 12.8.2, may obscure any part of the wheel when viewed from the outside of the car towards the car centre line along the axis of the wheel.

    Articles 12.8.1-2 says that:
    12.8.1 The only parts which may be physically attached to the wheel in addition to the tyre are surface treatments for appearance and protection, valves for filling and discharging the tyre, balance weights, drive pegs, tyre pressure and temperature monitoring devices and spacers on the inboard mounting face of identical specification on all wheels for the same axle.
    12.8.2 The wheel must be attached to the car with a single fastener. The outer diameter of the fastener must not exceed 105mm and the axial length must not exceed 75mm. The wheel fastener may not attach or mount any part to the car except the wheel assembly described in Article 12.8.1.

    So I can’t understand how any wheel cover as big as that on F10 could be legal.

    • Its because those relate to the wheel, in the eyes of the rules these parts are bodywork and relate to space allowed for brake ducts. It’s the same interpretation that allowed the fixed wheel fairings we saw last year

      • But 11.4 relates to the brake ducts and I don’t know if I understand it correctly, but I think that you can’t have any bodywork on the outer side of the wheel.

        BTW, Sam Michael said a few times that last years covers had quite a bad effect on the wake, do you think it applies to the new ones too?

      • The next thing is, if it’s allowed to have covers, why don’t they use similar pieces to last year? Because looking at that photo, is seems to me that the “cover” complies with article 12.4.5, which relates to the wheel. So isn’t it actually part of the wheel (co it would act like a cover, but it wouldn’t be static?

      • As I understand it the teams agreed to remove the fairings that did not spin with the wheel. This still leaves the teams able to add the fairings attached to the wheel.

  2. Just to confirm – the feet are not allowed past the front axle, and not ‘now allowed’ as in the article.

    Safety and all that.

    Great article. Cheers Scarbs.

  3. Excellent……….I’m new to your site, but found the analysis very informing, consequently you’ve been moved to the top of my bookmarks. Hope to follow your contributions in the future.

  4. Excellently written! When I buy my next passenger/ commercial car I’ll keep the weight distribution, wheelbase, etc in mind. Many thanks.

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