Small Wheels & Big Wheels - Why?

[RobJ]

I think they put the small front wheels on for access reasons. One is access to the engine. The other is access by the FEL, without interfering with the front wheels.

Ralph

Remember though the FEL came a long time after the first steam powered tractor.

Crawlers were popular for some time because of soil compation.

 

[ccsial]

My vote would be to save cost since the fronts mostly steer on the smaller tractors and as pointed out there is less load.

All the tractors with large front wheels I've seen are articulated which is even more cost. If the large front wheels turned tight like the small ones there would be a clearance issue. You would need a skinny front end or a real wide axle.

 

[Fast Eddie]

I believe the reason is that big wheels deliver more torque to move the tractor. It's sort of like using a long wrench to loosen or tighten a bolt.
Eddie

 

[radman1]

One of the biggest reasons for smaller front tire on tractors, is small tire is needed for tight turning radius without hitting the frame. This is a real problem on larger ag tractors. Some manufactures actually design the frames with a curve or rise to give more tire clearance. Important for row crop tractors which often have relatively narrrow tire width to fit between rows of crops. Most CUTs could probably have a somewhat larger tire on the front and still have good turning radius. Larger rear tire carries most of the weight with larger and heavier rear implements. The larger rear tire has more ground contact for traction. Big ag tractors have tall profile rear tires to get more ground contact and will last longer. 20-30 years ago the trend in ag tractors was to have wide rear tires for traction and less compaction. However, the wide tires won't fit between crop rows. Now rear tires are tall and relatively narrow.

 

[1948berg]

Here
Google Bilder-resultat for http://www.vintagetractorengineer.com/blog/wp-content/uploads/2007/10/county1184.jpg

 

[RoyJackson]

Large tires on the rear axle for maximum traction and reduced soil compaction.
Small tires on front to allow steering geometry for greater maneuverability.

This type of tractor design works great in smaller fields and orchards.

I'd suppose this is the same thought behind the tricycle type tractor.

Equal sized tires front and rear for maximum traction when pulling. The tradeoff is it takes a football field to turn. But on a 1000 acre field, the traction benefits outweigh the limited maneuverability. That's also when you really see the advantages of articulation. There's a lot of $$$$'s there though.