Guest Blog: Mat Oxley - Why inline-four MotoGP bikes handle better than V4 MotoGP bikes

MotoMatters.com is delighted to feature the work of iconic MotoGP writer Mat Oxley. Oxley is a former racer, TT winner and highly respected author of biographies of world champions Mick Doohan and Valentino Rossi, and currently writes for Motor Sport Magazine, where he is MotoGP correspondent. We are featuring sections from Oxley's blogs, which are posted in full on the Motor Sport Magazine website.


Why inline-four MotoGP bikes handle better than V4 MotoGP bikes

V4 MotoGP bikes make more power, inline-fours handle better. That’s why Johann Zarco, Jorge Lorenzo and others struggle when they switch from inline-fours to V4s

Speak to most MotoGP engineers and they will tell you that the two most important words in race-bike engineering are balance and compromise.

Pretty much whatever you do to improve one area of performance impairs another: you make the bike turn quicker and it becomes less stable, you increase peak power and you lose midrange and so on.

Therefore an engineer’s job is to compromise the positives and negatives, looking for a balance that maximises the positives and minimises the negatives.

This is just as important in the macro – the basic design of the motorcycle – as the micro – a few clicks of damping or a half millimetre change to the ride height.

Both MotoGP engine configurations – the V4 (Aprilia RS-GP, Ducati Desmosedici, Honda RC213V and KTM RC16) and the inline-four (Suzuki GSX-RR and Yamaha YZR-M1) – have their positives and negatives. In brief, a V4 engine produces more horsepower, while the inline-four allows better handling.

This much is obvious when we watch a MotoGP race: the inline-four swoops past through a corner, the V4 blasts past on the next straight.

One part of the motorcycle plays the biggest role in making V4s more powerful and inline-fours easier to handle: the crankshaft, specifically the length of the crankshaft.

A V4’s crankshaft is shorter, more rigid and runs on fewer bearings, which helps in the search for more power. An inline-four’s crankshaft is longer, which makes the bike more user-friendly through the corners.

“That’s why it’s the engine that gives an inline-four its superior line through corners, not the chassis,” says a former Yamaha engineer who now works for a rival factory.

But why?

Read the rest of Mat Oxley's blog on the Motor Sport Magazine website.

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Comments

One thing I wonder is what made the Ducati seemingly a little easier for Lorenzo to adapt to than the Honda?  Maybe the longer wheel base, making the front end a little more stable (though harder to turn in)? 

When GP 500 went to MotoGP they made a rule that gave motorcycles with 4 or 5 cylinder engines the same weight. Only Honda saw the opportunity to build a V5 with one cylinderbank with 2 cylinders and one with 3 cylinder.  When MotoGP went to 800cc that rule dissapeared but the idea of having different numbers of cylinders in a V-engine could make a comeback...  Imagine a V3-1. 3 cylinders in one row and one single cylinder to the rear sharing crankpin with the second cylinder on the front cylinder block ( or mabye the 1st cylinder, who knows :) ).  If the engineers could solve the vibrations that would be the perfect mix between an inline 4 and a V-four....   And no.. I have ever read or heard about an engine like this so you read it here first... :)

Interesting idea. And outside the box.

A 3cyl Superbike seems a missed opportunity in the era just before this one when electronics were minimal and tire wear a struggle. Now? Not so sure, but the 765 Moto2 is well established as a good big step forward from the 600 inline 4. Keep your electronics, punch it out just a bit further to 800-900cc, and happily I will watch your NASA bikes leave me here forever in a conventional optimized sweet spot.

...but the memories in the paddock of the FP1 probably saw fit to no one being in a rush to go there again. ;)