384 CAERIAGES. 



much to their strength and durability. A light wheel for 

 road wagons, 4 feet in diameter, should dish about f to I 

 inch ; and coach wheels, 3 ft. 6 in. in diameter, should dish J 

 inch, the measurements being taken, in both cases, after the 

 tire has been set. 



The Tire. — It is upon this part of the wheel that most 

 of the wear comes, and if defects exist here, no excellence 

 in the other parts will be of any avail. The important 

 points in a good tire are, that it should be made of good 

 iron, that it should be the size best adapted to the vehicle 

 on which it is to be used, and that it be "set" well, nei- 

 ther so tight as to draw the wheel out of shape, or so 

 loose as to allow any racking of the spokes. The tires 

 should be made of Ulster iron, or the best English re- 

 fined iron. Ordinary steel tires, though thrice as durable 

 as iron, are apt to snap in frosty weather. Imported 

 *' homogeneous" steel is now being successfully used in 

 light vehicles; but its cost (16c. per lb.) precludes its 

 use on heavy wheels. It is very durable, and remarkably 

 tough. 



Flat tire is the best for all purposes ; convex tire is 

 satisfactorily used on the flat, hard roads of Europe, but 

 they are not adapted to American use. Heavy tire on 

 light rimmed wheels is objectionable, for the reason that it 

 breaks down the felloes. All tires yield, more or less, to 

 sudden concussions; if heavy, it retains its bent form, 

 while, if light, it is forced back to its proper position by 

 the spring of the felloes. Wide tires are desirable on soft 

 roads, being less likely to cut in (causing the carriage to 

 run heavily, and injuring the road,) than narrower tires. 

 All tires should be fastened on with bolts, one between 

 each two spokes. 



